Seminars 2012

Title: Plasmonic Harvesting of Solar Energy for Chemical Reactions
Speaker: Professor Jianfang Wang
Date: 20 December 2012
Time: 3pm - 4pm 
Venue: MAS Executive Classroom 1 (MAS-03-06)
Host: Assistant Professor Xiong Qihua
 Abstract:The efficient use of solar energy has received wide interests due to the increasing energy and environmental concerns. In addition to the tremendous efforts made on improving the efficiencies of photovoltaic and solar heating devices, the exploration of new solar energy harvesting means will also have long-term impacts. A potential way in the field of chemistry is sunlight-driven catalytic reactions. In this presentation, I will report on the direct harvesting of light from the visible to near infrared region for chemical reactions by use of plasmonic Au Pd nanostructures, which serve simultaneously as an energy converter and a catalyst for Suzuki coupling reactions. The plasmonic excitation enables and accelerates the targeted catalytic reaction through plasmonic photocatalysis and plasmonic photothermal heating. The intimate integration of the plasmonic energy converter and the catalyst facilitates the efficient light energy conversion and utilization. The effect of plasmonic photocatalysis becomes more important when the incident light is at the plasmon resonance wavelength or the resonant incident light power is increased.

 

Title: Probing size-dependent light-matter interactions and structural phase change properties with nanowires
Speaker: Professor Ritesh Agarwa
Date: 19 December 2012
Time: 11am - 12pm
Venue: Hilbert Space (SPMS-PAP-02-02)
Host: Assistant Professor Xiong Qihua
 Abstract:Semiconductor nanowires offer a unique approach for the bottom up assembly of electronic and photonic devices with the potential of integrating different technologies on a common platform. The one-dimensional geometry allows efficient transport of charged carriers, photons and phonons in a highly directed manner. In addition, the anisotropic geometry and mesoscopic length scales of nanowires also makes them very interesting systems to study a variety of size-dependent phenomena. We will discuss the intriguing size-dependent properties of one-dimensional semiconductor nanowires at the 20-200 nm length scales. At these length-scales not only finite-size effects become important, but also other length-scales such as visible optical wavelengths, strain fields, interfacial, and polarization scales become comparable to the size of the nanostructures. Proper understanding of these phenomena and the effect of different length scales on nanowire properties becomes important, which is also required to rationally design functional devices with tunable and precisely controlled responses.

We will discuss different examples: size-dependent interaction of light within nanowire optical cavities and their very unique waveguiding and slow-light propagation properties; nanowires integrated with plasmonic nanocavities allows precise control over their excited state lifetimes, which can be shortened by more than three orders of magnitude to sub-picoseconds due to strong confinement of the optical fields based on the surface plasmon whispering gallery modes; size-dependent electrical properties that lead to structural phase change phenomena, which are very important for new types of nonvolatile memory devices. None of these phenomena exists in bulk systems or in extremely small systems with sub-10 nm sizes. Our recent efforts to observe the crystalline to amorphous phase change in “real time” via in situ electron microscopy techniques will be discussed, which allows unprecedented insights into the critical events that lead to structural phase transformations. The unique aspects of each sizedependent phenomenon in nanowires will be explained with the help of simple models. The implications of these findings for assembling novel and reconfigurable electronic and photonic devices will be discussed.

 

Title: The work value of information - recent advances
Speaker: Dr Oscar Dahlsten
Date: 11 December 2012
Time: 3pm - 4pm
Venue: Hilbert Space (SPMS-PAP-02-02)
Host: Assistant Professor Tomasz Paterek
 Abstract:I discuss the relationship between information and work, which has been much debated ever since Maxwell first conceived of his daemon that uses information to turn 'heat' into 'work'. It is both of conceptual and technological interest. I argue that this relationship is best quantified using a new operationally motivated approach to information theory known as the single-shot approach. This is as opposed to the standard Shannon/von Neumann entropy approach. The two approaches differ dramatically when there are significant fluctuations around the average work, but coincide in certain limits. There is now a series of papers on this topic; I will try to give the key points.

 

Title: Multi-component Bosons in Optical Lattices
Speaker: Professor George Batrouni
Date: 29 November 2012
Time: 4pm - 5pm 
Venue: Hilbert Space (SPMS-PAP-02-02)
Host: Assistant Professor Pinaki Sengupta
 Abstract:Using Quantum Monte Carlo simulations and Mean Field Theory, we study the ground state and finite temperature phase diagrams of multi-component bosons loaded in optical lattices. In particular, we focus on the spin-1/2 bosonic model and study its phases in the ``ferromagnetic'' and ``antiferromagnetic'' cases. Related models are briefly discusses.

 

Title: Device-independent quantum information
Speaker: Professor Valerio Scarani
Date: 15 November 2012
Time: 4pm - 5pm
Venue: Hilbert Space (SPMS-PAP-02-02)
Host: Associate Professor David Wilkowski
 Abstract:Bell's inequalities can be seen as a family of entanglement witnesses, with a very special property: they detect entanglement without need of prior knowledge on the nature of the system or the measurements. For this reason, they can be used for ``device-independent" assessment.
In this talk, I shall review the main results in device-independent quantum cryptography, randomness generation and assessment of the quality of a source of entangled pairs (a.k.a. selftesting). Then I shall present in some detail some of our recent results in this field.

 

Title: Developing a TEM-based Laboratory for Nanoresearch
Speaker: Professor Litao Sun
Date: 7 November 2012
Time: 10.30am - 11.30am 
Venue: Hilbert Space (SPMS-PAP-02-02)
Host: Assistant Professor Yu Ting
 Abstract:With the continuous improvement of in situ techniques inside transmission electron microscope (TEM), the capabilities of TEM extend beyond structural characterization to high-precision nanofabrication and property measurement, which not only enriches the experimental methods and broadens the application field of TEM, but also provides new opportunities for the development in nanoscience and nanotechnology. Based on the idea of "setting up a Nano lab inside a TEM", we present our recent progress in dynamic in situ electron microscopy including in situ growth of nanomaterials, nanofabrication with atomic resolution, in situ property characterization and nanodevice construction.

Publications：
• Science 312, 1199 (2006)；
• Nature Nanotechnology 2, 307 (2007);
• Phys. Rev. Lett. 101, 156101 (2008)；
• Phys. Rev. Lett. 105, 196102 (2010)；
• Advanced Materials 24, 1844 (2012);
• Advanced Materials 24, 5124 (2012);
• Adv. Funct. Mater. DOI: 10.1002/adfm.201200888 (2012) ;

 

Title: Three-Dimensional Topological Insulators: Probing Spin Polarized Surface States and Perspective for Future Spintronics
Speaker: Professor Akio Kimura
Date: 31 October 2012
Time: 4pm - 5pm
Venue: Hilbert Space (SPMS-PAP-02-02)
Host: Assistant Professor Wang Lan
 Abstract:Three-dimensional topological insulators (3D TIs) with a gapless topological surface state (TSS) in a bulk energy gap induced by a strong spin-orbit coupling have attracted a great deal of attention as key materials to revolutionize current electronic devices. A spin helical texture of a TSS, where the electron spin is locked to its momentum, is a manifestation of a 3D TI.

A number of well-known thermoelectric and phase-change materials have so far been predicted to be 3D TIs. In order to experimentally confirm their topological natures, spin- and angle- resolved photoemission spectroscopy (SARPES) is one of the most powerful tools and actually it has been playing major roles in finding some real 3D TIs [1]. Among the established 3D TIs, Bi2Se3 and Bi2Te3 have been most extensively studied because of their relatively large energy gap and the simplest TSS. However, the topological nature is apparently obscured near and below the Dirac point, which is disadvantageous for spintoronic applications.

In this seminar, some of the new ternary 3D TIs such as TlBiSe2 [2], GeBi2Te4 [3], Bi2Te2Se, Bi2Se2Te [4] are shown to possess spin polarized TSSs with marked spin polarizations, which are persistent even below the Dirac point. The availability of both upper and lower TSSs promises to extend the variety of spintoronic application, for instance, to the dual gate TI device and the topological p-n junction.

References
[1] M. Z. Hasan et al., Rev. Mod. Phys. 82 (2010) 3045.
[2] K. Kuroda, M. Ye, A. Kimura, S. V. Eremeev, E. E. Krasovskii, E. V. Chulkov, Y. Ueda, K. Miyamoto, T. Okuda, K. Shimada, H. Namatame, and M. Taniguchi, Phys. Rev. Lett. 105 (2010) 146801.
[3] K. Okamoto, A. Kimura et al., arXiv: 1207.2088 (2012).
[4] K. Miyamoto, A. Kimura, T. Okuda, H. Miyahara, K. Kuroda, H. Namatame, M. Taniguchi, S. V. Eremeev, T. V. Menshchikova, E. V. Chulkov, K. A. Kokh, and O. E. Tereshchenko, Phys. Rev. Lett. 109, 166802 (2012).

 

Title: Molecular Functional Materials: From Multistability to Energy Transfer
Speaker: Professor Anna Painelli
Date: 18 October 2012
Time: 11am - 12pm
Venue: Hilbert Space (SPMS-PAP-02-02)
Host: Assistant Professor Cesare Soci
 Abstract:The properties of functional molecular materials are profoundly affected by the interaction of each molecule with the surrounding medium. Cooperativity emerges in these systems from the interaction of delocalized electrons within each molecular unit with molecular vibrations and with local electric fields generated by the local environment. Essential state models have been recently proposed for different families of functional chromophores: accounting for just few diabatic electronic states, the models provide a simple and coherent theoretical framework to rationalize (low-energy) linear and non-linear optical spectra of families of compounds. Functional chromophores are characterized by large (hyper)polarizabilities, making polar solvation a highly cooperative phenomenon. Unconventional inhomogeneous broadening due to polar solvation eventually results in ground- or excited-state symmetry breaking in nominally symmetric chromophores, including cyanine-dyes. Nonadiabatic essential-state models rationalize the highly non-trivial spectroscopic behavior of these systems [1]. Essential-state models, developed for chromophores in solutions, successfully describe interacting molecules [2]. Cooperativity in clusters of chromophores is mainly driven by electrostatic interactions: its extreme manifestation is recognized in multistability [3] and multielectron transfer [4]. The same interactions are also responsible for resonant energy transfer, and are accurately described by essential-state models [5], opening the way to models for energy transfer fully accounting for the non-adiabatic molecular vibrations and for inhomogeneous broadening due to polar solvation.

References:
[1] F. Terenziani et al., J. Phys. Chem. Lett.2010, 1, 1800–1804; J. C ampo et al. J. Am. C hem. Soc. 2010, 132, 16467, C . Sissa et al., Chem. Phys. Chem., in press.
[2] F. Todescato et al. Phys. Chem. Chem. Phys 2011, 13,11099; L. Grisanti et al., J. Phys. C hem. B, 2011, 115, 11420.
[3] G. D'Avino et al., J. Am. Chem. Soc. 2008, 130, 12065.
[4] A. Painelli, F. Terenziani, J. Am. Chem. Soc. 2003, 125, 5624.
[5] C . Sissa et al. Phys. Chem. Chem. Phys. 2011, 13, 12734.

 

Title: Quantitative Research Opportunities in JPMorgan
Speaker: Dr Shen Ning
Date: 17 October 2012
Time: 3pm - 4.30pm
Venue: SPMS - LT3 (SPMS-03-02)
Host: Assistant Professor Cheong Siew Ann
 Abstract:We’re proud of our firm’s 200-year history and our well-established reputation for doing first-class business in a first-class way. Today’s markets have made our Quantitative Research function more important than ever before. We need well-rounded quant professionals who can understand and analyse the numbers. Working strategically across the business, you’ll play a critical role in shaping J.P. Morgan’s thinking. We have attractive opportunities for interns – the high quality of internship projects are often used in Masters or Doctoral theses. Be part of it.

Quantitative Research is an expert modelling group at J.P. Morgan and an unchallenged leader in financial engineering, derivatives modelling and risk management. Focusing on product innovation, hedging and control, the group works with traders, marketers and risk managers across all geographical regions and asset classes.

The Quantitative Research team develops and maintains sophisticated mathematical models, cuttingedge methodologies and infrastructure that are used to value and hedge financial transactions, ranging from flow products to complex derivatives. It develops portfolio risk measurement methodologies as well as works on models for economic capital, and credit and market risk exposures.

Your role in Quantitative Research will be varied. It could include developing mathematical models for pricing, hedging and risk measurement, or supporting trading activities by explaining model behaviour or implementing risk measurement and valuation models, to name just a few.

With a team of over 350 Quantitative Research professionals across 5 continents, J.P. Morgan provides a truly unique global platform.

 

Title: Optical imaging of complex fields based on the use of azobenzene nanomotors
Speaker: Professor Jérôme Plain
Date: 11 October 2012
time: 4pm - 5pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Xiong Qihua 
 Abstract:We introduced a technique based on a molecular photomotor to probe the optical near field of metal nanoparticles. The approach relies on photo-isomerization-based matter migration of azobenzene molecules in the vicinity of metal nanoparticles. The matter migration is characterized by AFM and gives insight into near-field features related to the metal particles. The method turned out to be sensitive to both the intensity and the polarization state of the involved near-field. In parallel, we developed a model allowing for the understanding of the material response and migration. I will present the last results obtained using this technique from a theoretical and experimental points.

 

Title: The Physical Review Journals and You: Why and how should we work together?
Speaker: Dr Manolis Antonoyiannakis
Date: 10 October 2012
Time: 11am - 12pm
Venue: Hilbert Space (PAP-02-02)
Host: Associate Professor Claus-Dieter Ohl
 Abstract:The Physical Review family journals (PRL, PRA, PRB, PRC, PRD, and PRE) of the American Physical Society (APS) are the bedrock journals that the international physics community relies on. But, they need the community's support and contributions to maintain their strengths. Our talk will address the question of why, and how, the journals and the physics community should work together more actively and effectively.

We will first briefly discuss the journals' status and their multifaceted contribution to physics and to the international physics community. Then we will zoom in on the editorial and peer-review process and give you an insider's view of the APS editorial system: How do the editors evaluate new papers, choose referees, and accept and reject papers? How do they select which papers to highlight in the exclusive online platform /Physics/ or as Editors' Suggestions? We will also discuss how you can maximize your chances of publishing your work in the APS journals and how you can make your scientific expertise and views really count by serving as a referee. Finally, we will provide representative statistics on publications, citations and impact measures, and make some geographic and institutional comparisons along the way.

Last May, the APS launched a new, broad-scope, fully open-access, and highly selective journal, Physical Review X ( http://prx.aps.org/ ). What is PRX's mission? What can the new journal offer you? We'll answer these questions and others that you may have.

Last but not least, we want to get your feedback on the Physical Review journals and our editorial work. Such feedback will help the journals become stronger and work better for you.

 

Title: Fibre Amplifiers, the Fiberglass Web and the Optical Moore’s Law
Speaker: Professor Emmanuel Desurvire
Date: 20 September 2012
Time: 2pm - 4pm
Venue: SPMS-LT2 (SPMS-03-03)
Host: Assistant Professor Fan Hongjin
 Abstract:Since the 1966 prediction by C.Kao regarding the possibility of achieving optical telecommunications though silica-glass fibres, lightwave systems have known about a half-century of explosive growth. Their rapid deployment across continents and oceans, forming altogether a Fibreglass Web, made possible the implementation of today’s Internet. Yet, such a paradigm would not have been possible without another 1988/1989 discovery : the possibility of in-line optical regeneration though Er-doped fibre amplifiers (EDFA), with multi-THz optical bandwidth and practical laser-diode pumping. With rapid progress on wavelength-division multiplexing (WDM) technologies, the capacity-distance product (Bit/s/km) impeccably followed a new Optical Moore’s Law (OML) steadily exhibiting a tenfold increase every 4 years, over a period of at least 30 years. Alas, the last decade is consistently showing that the OML must be revisited for its self-predicting promises. Within 20 years, if not earlier, should we be possibly witnessing the end of this serendipitous Era of bandwidth transparency ?

 

Title: Nonlinear dynamics of Bose-Einstein condensates in periodic potentials
Speaker: Dr Elena Ostrovskaya
Date: 14 August 2012
Time: 3pm - 4.30pm
Venue: Hilbert Space (PAP-02-02)
Host: Associate Professor Ivan Shelykh
 Abstract:Dynamics of Bose-Einstein condensates confined in optical or magnetic traps with spatial periodicity is one of the most vigorously studied topics in quantum-atom optics. Due to the unprecedented degree of experimental control over parameters of the system, condensates in reconfigurable periodic potentials created by optical lattices offer a wide variety of opportunities for fundamental research. In this talk I will give an overview of the effects that occur due to the interplay of the inherent nonlinearity of atomic condensates produced by atomic collisions and periodicity of the atom trapping potentials created by optical lattices. I will describe nonlinear localization and transport of Bose-Einstein condensates in optical lattices, discuss state-of-the-art experimental investigations of these effects, and draw parallels with the behaviour of coherent light waves in periodic photonic structures.

 

Title: Formation of Planetary Systems - Observations, Models, Experiments
Speaker: Professor Dr Juergen Blum
Date: 13 August 2012
Time: 4pm - 5pm
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Pinaki Sengupta
 Abstract:Since the discovery in the year 1995 that planets around other stars do exist, astronomers have detected signals from more than 700 extrasolar planets. A comprehensive theory about the origin of planetary systems must explain the formation of our own Solar System as well as that of some very strange new worlds. In my presentation, I will review the scientific findings about the different stages of planet formation, from microscopically small dust grains to fully grown up planets. Combining the results of laboratory experiments, theoretical astrophysics, and observations of stars hosting planets, allows us – for the first time – to draw the overall picture of the formation of planetary systems.

 

Title: Recent Trends in Ultrafast Laser Science
Speaker: Dr Ian Read
Date: 19 July 2012
time: 11am - 12pm
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Sun Handong 
 Abstract:Since its introduction, chirped pulse amplification of ultrashort pulses has undergone many significant improvements. Titanium sapphire amplifiers can now produce pulse energies > 50mJ without the need for cryogenic cooling and with pulse durations as short as 25fs. These broad capabilities have enabled several important applications in biology, chemistry and physics. Most recently, ultrafast lasers have become more user-friendly – utilizing ‘hands-free’ strategies to further enhance the laser system’s stability. This presentation will review these technologies and discuss future trends

 

Title: Structural Biology of Small RNA-mediated Gene Regulation and Methylationmediated Epigenetic Regulation
Speaker: Professor Dinshaw J. Patel
Date: 19 July 2012
Time: 10.30am - 11.30am
Venue: SBS Classroom 2 (SBS-01n-22)
Host: Associate Professor Phan Anh Tuan
 Abstract:The RNA segment of the lecture will focus on the structural biology of riboswitches, mRNA elements consisting of a sensing domain and an expression platform, that undergo conformational changes on metabolite binding, and utilize on-off switches to control gene expression. This segment will be followed by our recent research on the structural biology of Argonaute and Dicer proteins and emerging mechanistic insights into cleavage events associated with RNA silencing. The chromatin segment of the lecture will describe recently determined structures of productive and autoinhibitory DNMT1-DNA complexes, thereby formulating a two-state model of eukaryotic maintenance DNA methylation. Finally, we shall outline our structural studies of readers and erasers of histone marks and the impact of small molecules that perturb these epigenetic regulation processes.

 

Title: Advances in Characterization of Graphene-related Nanomaterials Using Atomic Force Microscopy
Speaker: Dr Yu Jing Jiang
Date: 12 July 2012
Time: 4pm - 5pm
Venue: Hilbert Space (PAP-02-02)
Host: Professor Shen Ze Xiang
 Abstract:Current state of atomic force microscopy (AFM) imaging of graphene and its derivatives will be reviewed. The emphasis will be made on exploring their exotic electric properties. For example, potential applications of graphene as ultrathin transistors, sensors and other nanoelectronic devices require them supported on an insulating substrate. Therefore, a quantitative understanding of charge exchange at the interface and spatial distribution of the charge carriers is critical for the device design. Here, we demonstrate that AFM-based technique Kelvin force microscopy (KFM) can be applied as an experimental means to quantitatively investigate the local electrical properties of both single-layer and few-layer graphene films on silicon dioxide. The effect of film thickness on the surface potential is observed. Our measurements indicate that a 66 mV increase in the surface potential is detected for an eleven-layered film with respect to a nine-layer film. Furthermore, with the introduction of multiple lock-in amplifiers (LIAs) in the electronics for scanning probe microscopes, single-pass kelvin force microcopy and probing of the other electric property such as local dielectric permittivity via the capacitance gradient dC/dZ measurements are allowed by the simultaneous use of the probe flexural resonance frequency ωmech in the first LIA targeting the mechanical tip-sample interactions for surface profiling, and a much lower frequency ωelec (both in the second LIA and its second harmonic in the third LIA) for sample surface potential and dC/dZ measurements, respectively. In contrast to surface potentials, the dC/dZ measurements show that local dielectric permittivity of few-layer graphene films maintains at the same level regardless of the film thickness. Such simultaneous monitoring of multiple electronic properties that exhibit different behaviors in response to the graphene layers provides us a technique to achieve both a comprehensive characterization and a better understanding of grapheme materials. In addition, new results on investigations of other graphene-related systems such as white graphene (Boron Nitride) and graphene oxide (GO) will be presented.

 

Title: Asymmetric Heat Conduction and Negative Differential Thermal Resistance in Nonlinear Systems
Speaker: Professor Bambi Hu
Date: 10 July 2012
Time: 4pm - 5pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Chew Lock Yue
 Abstract:Heat conduction is an old yet important problem. Since Fourier introduced the law bearing his name 200 years ago, a first-principle derivation of this law from statistical mechanics is still lacking. Worse still, the validity of this law in low dimensions and the necessary and sufficient conditions for its validity are still far from clear. In this talk we’ll report on our recent works on asymmetric heat conduction and negative differential thermal resistance. The dependence on the system size, the coupling constant and the thermodynamic limit will be discussed.

 

Title: Free-electron-driven nanoscale light sources: from Hertzian antennas to metamaterials
Speaker: Dr Giorgio Adamo
Date: 10 July 2012
Time: 11am - 12pm
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Cesare Soci
 Abstract:Nanoscale light sources for future integrated photonic circuits are a key element in nanophotonics research today. Our group has been investigating an unconventional approach towards the development of nanoscale optical sources: the use of free electron beams to pump optical sources.

Here the demonstration of three types of nanoscale light sources with increasing degree of complexity will be shown: a nanoscale optical antenna, a FEL-like tuneable nanoscale light source and a metamaterial-based spatially coherent light source.

 

Title: Metal Oxide Quantum Rod & Dot- based Structures & Devices: Aqueous Design, Electronic Structure & Applications for Solar Energy Conversion
Speaker: Professor Lionel Vayssieres
Date: 9 July 2012
Time: 11am - 1pm 
Venue: MAS Executive classroom 1 (MAS-03-06)
Host: Assistant Professor Fan Hongjin 
 Abstract:The demand of novel functional materials has become the major challenge scientists face to answer crucial contemporary issues such as alternative energy sources, novel sensors for a safer and cleaner environment and for better health. For instance, one of the promising alternatives for the transition of energy resource from its fossil fuel based beginning to a clean and renewable technology relies on the widespread implementation of solar-related energy systems, however the high cost of energy production and low-energy of currently used material combinations pose an intrinsic limitation. In this context, revolutionary materials development is required to achieve the necessary dramatic increases in power generation and conversion efficiency. The necessity of materials development which is not limited to materials that can achieve their theoretical limits, but makes it possible to raise theoretical limits by changing the fundamental underlying physics and chemistry is crucial. Low cost purpose-built, functional materials with optimized geometry, orientation, and aspect ratio combined with inexpensive large scale manufacturing methods will play a decisive role in the success of materials for renewable energy. However, fabricating and manufacturing large area of such functional materials is a daunting challenge. Novel smarter and cheaper fabrication techniques and, just as important, better fundamental knowledge and comprehensive understanding of materials and their syntheses as well as their properties using nanoscale phenomena such as quantum confinements to create multifunctional structures and devices is the key to success. R&D exploiting Nanoscience and Nanotechnology has the greatest potential to reach such challenging goals. Such ideas will be demonstrated by the thermodynamic modeling, low-cost aqueous design and fabrication of highly oriented crystalline arrays of metal oxide quantum dots and rods-based structures and devices with controlled orientation, size and shape onto various substrates designed at nano-, meso-, and micro-scale by aqueous chemical growth at low-temperature. In addition, the in-depth characterization of their electronic structure and quantum confinement performed at synchrotron radiation facilities and their applications for solar hydrogen generation, photovoltaics, magnetic and gas sensor devices will be presented.

 

Title: CZTSSe: An emerging high performance solar cell technology
Speaker: Dr Oki Gunawan
Date: 6 July 2012
Time: 10am - 11am 
Venue: SPMS-LT5 (SPMS-03-08)
Host: Professor Alfred Huan 
 Abstract:Photovoltaics (PV) technology is one of the leading candidates for large scale and renewable energy source in the near future. At IBM, we recently developed kesterite Cu2ZnSn(Se,S)4 (CZTSSe)-based solar cell, an emerging thin film PV technology unrestrained by material availability or toxicity issues suffered by other leading technologies such as CuInGaSe (CIGS) and CdTe. We recently demonstrated a CZTSSe cell with world record efficiency of 10.1% and performed various electrical characterization techniques to identify the key performance bottlenecks. I will draw various comparisons between CZTSSe and the well established CIGS technology to gain insights to the current performance limitations in CZTSSe. These findings help to identify key areas of improvements to realize a high performance, tera (1012) watt scale CZTSSe PV technology in the near future.

 

Title: Designing and Synthesizing Materials at the Nanoscale for Advanced Energy Applications
Speaker: Professor Dunwei Wang
Date: 6 July 2012
Time: 11am - 1pm 
Venue: MAS Executive classroom 1 (MAS-03-06)
Host: Assistant Professor Fan Hongjin 
 Abstract:How to significantly advance energy conversion and storage technologies, such as solar cells, solar fuel production from water splitting, and batteries, represents a key challenge faced by the scientific community. At the heart of the problem is our inability to tailor certain aspects of materials’ intrinsic properties without adversely altering others. As a result, researchers are currently working within serious constraints. Recent advances in materials research, particularly those focusing on morphology innovations at the nanoscale, may offer solutions to this problem at a fundamental level. Here, we present our recent efforts and some positive results toward this direction. We proposed and tested the idea of forming heteronanostructures, various parts of which can be purpose-designed independently. When combined together, these different parts contribute to the overall functionality in a complementary fashion, yielding materials with properties that have not been observed on simple structures. We will introduce the research within the context of a nanonet-based design, which is enabled by a unique two-dimensional crystalline material we discovered. We show that the nanonet solves the low conductivity problem many metal oxide semiconductors and battery electrode materials have. The resulting nanostructures exhibit better performance in solar water splitting and battery applications than their non-heteronanostructure counterparts do. A new door to electrode design for improved energy applications may be opened up by this approach.

 

Title: Synthesis, Study and example of Implementation of Inorganic Nanofilaments
Speaker: Professor Vincent SALLES
Date: 5 July 2012
Time: 3pm - 4pm
Venue: MAS Executive classroom 1 (MAS-03-06)
Host: Assistant Professor Fan Hongjin 
 Abstract:A growing interest is given to electrospun nanofibers (NFs) for new potential applications in fields as large as textile industry, nanomedicine, food industry, etc. New generation materials can be designed and then used in order to improve some specific properties according to the desired application. In the field of ceramics, many studies are dedicated to the elaboration of oxides, i.e. Al2O3 , TiO2 and SnO2 for instance, but one-dimensional non-oxide ceramics are less studied despite their high application potentiality.

In this talk, I will detail how to prepare boron- and iron-based 1D nanostructures obtained from specific precursors and polymers, with a controlled shape and a high purity. The nature of the final materials is changed by varying the compositions of the starting boron-based polymers. An example of actuator application will be given with iron carbide filaments, used as fillers in a polymer matrix to enhance the electrostricitve properties of the electroactive polymer.

 

Title: Conformal Transformation Optics
Speaker: Professor Huanyang Chen
Date: 4 July 2012
Time: 2pm - 3pm 
Venue: MAS Executive classroom 1 (MAS-03-06)
Host: Assistant Professor Zhang Baile 
 Abstract:Transformation optics, as a powerful tool, can be utilized to design various devices with novel properties. However, such devices are usually anisotropic and of magnetic response, hence a great challenge to design and fabricate. Optical conformal mapping, although not the main branch of transformation optics, can be used to design devices with isotropic materials, and of non-magnetic response, thus easy to implement. In this talk, I will show some recent designs in my group, including invisibility cloak, perfect lens and conformal lens (that can manipulate the numbers of light sources). Devices like carpet cloak from quasi-conformal mapping (a numerical method, and resemble optical conformal mapping), have won great progress and been realized from microwave frequencies all the way to optical frequencies. Therefore, more efforts could be made to conformal transformation optics.

 

Title: Transforming Light and Sound With Metamaterials
Speaker: Professor Nicholas Xuanlai Fang
Date: 3 July 2012
Time: 4pm - 5pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Zhang Baile 
 Abstract:Recently, exciting new physics and applications are emerging from metamaterials made of artificial “atoms” and “molecules”. These metamaterials has inspired a series of key explorations to manipulate, store and control the flow of energy at unprecedented dimensions. Yet, these ground-breaking achievements are only the tip of the iceberg, where the next-generation metamaterials, incorporating unique topological interactions between waves and matter, are waiting to be discovered.
In this talk, I will discuss our progress of fabrication and characterization of these optical and acoustic metamaterials. We demonstrated, for the first time, focusing and rerouting ultrasound through broadband and highly transparent metamaterials. We also observed a set of localized modes in optical metamaterials, using novel near field optical and electron probes. These novel metamaterials, could be the foundation of broadband photo-absorbers, directional emitters, as well as compact and power-efficient devices in highly parallel optical networks.

 

Title: Complex Oxide Thin Films Grown by Laser Ablation: Metastable phases and Superlattice Structures
Speaker: Dr Wilfrid Prellier
Date: 3 July 2012
Time: 3pm - 4pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Tom Wu
 Abstract:Thin films and artificial heterostructures offer excellent opportunities to manipulate the strain and chemical heterogeneity in order to exhibit completely new or enhance the properties, which were absent in the parent compounds. It is for example possible to overcome the natural preference for disorder or lowdimensional ordering in certain materials by controlling the location of cations. It is also possible using the substrate-induced strain to stabilize metastable phases with unusual electronic properties Consequently, there has been recently growing interest in tailoring materials in thin films forms, having original properties that cannot be obtained in the form of bulk materials, using the process of the pulsed laser deposition technique. In this talk, I will illustrate the above approach by presenting the growth and characterizations of technologically important novel oxides. In particular, I will our recent work on superconducting super lattices, [1] as well as the observation of incipient ferroelectricity in CaMnO3 thin films. [2]

[1] D. Di Castro et al., arXiv:1107.2239 (2012).
[2] T. Gunter et al., Phys. Rev. B 85, 214120 (2012)

 

Title: Optical, Electronic and Magnetic properties of Low-Dimensional Nanomaterials
Speaker: Professor Arnaud Brioude
Date: 3 July 2012
Time: 3pm - 4pm 
Venue: MAS Executive classroom 1 (MAS-03-06)
Host: Assistant Professor Fan Hongjin
 Abstract:Low-dimensional nanomaterials have attracted much more attention in the past decades due to their special optical, electronic and magnetic properties and also potential applications in energy and environment. In this seminar, I plan to talk about the research findings in our laboratory in view of the 0D and ID nanomaterials, such as metallic silver, gold and semiconductor SiC, BN and Fe203 with various shapes and sizes, as well as different functional properties. In addition, Discrete Dipolar Approximation (DDA) simulation method will be discussed in my talk how to fundamentally understand the optical properties of metallic nanoparticles.

 

Title: Self-organization of atomic structures on metal surfaces
Speaker: Professor Haifeng Ding
Date: 29 June 2012
Time: 11am - 12pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Tom Wu
 Abstract:Atoms are the building blocks of all materials. The control of the geometric, electronic, and magnetic properties of arrays of atomic-scale structures provides the model systems for the understanding and fabrication of new materials and devices. In this talk, we will present our recent efforts for the understanding of the self-organization mechanism of atomic superlattice as well as for the creation of the novel atomic materials utilizing the substrate engineering and the quantum confinement. In combination with low temperature scanning tunneling microscopy measurements and the kinetic Monte Carlo simulations, we identified the self-organization mechanism of two dimensional atomic superlattice. With the substrate modification, semi one dimensional atomic structures like atomic strings can be created. Further we show quantum confinement can have strong influence on the adatom selforganization, resulting novel material design at atomic scale.

These works are supported by NSFC and MOST.

 

Title: Deep and Inelastic neutron scattering of quantum particles in ice, normal and metastable phases of water
Speaker: Professor Carla Andreani
Date: 28 June 2012
Time: 4pm - 5pm 
Venue: MAS Executive classroom 1 (MAS-03-06)
Host: Assistant Professor Pinaki Sengupta
 Abstract:The proton momentum distribution is a very sensitive probe of the potential of mean force experienced by the protons in hydrogen-bonded systems which can be accessed by deep inelastic neutron scattering experiments (DINS). DINS investigations complement x-ray and neutron studies on spatial distributions of the proton.

This talk presents DINS results on H quantum particles in polycrystalline ice [1], preliminary result from DINS on O quantum particles in heavy water and ice, and DINS and INS experiments in metastable ( supercooled) and stable (supercritical) phases of water. The experiments are motivated by the need of collecting quantitative and complementary information on both S(Q,E) and n(p) in a wide range of thermodynamic states in stable and metastable phases of water.

The DINS experiment on heavy water and ice is motivated by theoretical prediction of a considerable quantum excess in kinetic energy for oxygen atoms in ice at 269 K, i.e. 21 meV above the classical value of 35 meV. The INS experiment on supercooled water is motivated by the need to complement DINS experiment in metastable phase of water with vibrational spectra in the same system. The experiments on supercritical water, part of series of experiments (DINS, INS and Monte Carlo simulation), aim to explore the detail the momentum distribution S(Q,E) and n(p) in a thermodynamic range at~25 MPa in a temperature range 280° - 600°C, where density decreases from over 600 kg/m3 to less than 200 kg/m3 across the pseudo-critical temperature of 385°C.

Reference:
D. Flammini, A. Pietropaolo, R. Senesi, C. Andreani, F. McBride, A. Hodgson, M. A. Adams, L. Lin, and R. Car, J. Chem. Phys. 136, 024504 (2012); doi: 10.1063/1.3675838

 

Title: Magneto-elastic coupling and spin glass behavior in Gallium Ferrite
Speaker: Professor Rajeev Gupta
Date: 21 June 2012
Time: 4pm - 5pm
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Xiong Qihua 
 Abstract:Multiferroic and magnetoelectric materials have drawn significant attention from the scientific community owing to the underlying interesting physics and their potential in future spintronic device applications. Gallium ferrite (GaFeO3) or GFO is a ferrimagnet and a room temperature piezoelectric material whose ferri to paramagnetic transition temperature (Tc) can be tailored to room temperature and above by manipulating the Ga to Fe ratio, thus rendering GFO as a prospective single phase room temperature magnetoelectric system. In this talk I will present our recent results on probing magneto-elastic coupling in the ferrimagnetic state of single crystalline GFO studied using temperature evolution of phonons. Estimation of magneto-elastic coupling coefficient showed an abrupt change of coupling strength across ~200 K which could be attributed to spin reordering within the ferrimagnetic state. Analysis of frequency and dc field dependent ac susceptibility studies revealed that GFO undergoes a spin glass like transition at ~ 210 K consistent with possible spin rearrangement at ~ 200 K predicted by our Raman spectroscopic study. Such magnetic spin glass behavior in GFO has been discussed in terms of inherent cationic site disorder leading to geometrical frustration among the anti-ferromagnetically arranged Fe ions residing at Fe and Ga sites.

References: 1) S Mukherjee, A Garg and Rajeev Gupta, Journal of Physics: Condensed Matter, 445403(2011). 2) S Mukherjee, A Garg and Rajeev Gupta, Applied Physics Letters,112904 (2012)

 

Title: Pattern Formation from Competing Interactions: Implications for Soft and Hard Condensed Matter Systems
Speaker: Dr Charles Reichhardt
Date: 14 June 2012
Time: 4pm - 5pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Pinaki Sengupta
 Abstract:Pattern Formation from Competing Interactions: Implications for Soft and Hard Condensed Matter Systems I will give an overview of how systems with competing interactions such as repulsion on one scale and attraction on another can generically give rise rise to bubble, stripe, clump, and other patterns. The same patterns can occur for systems with purely repulsive interactions provided there are two or more distinct length scales in the potential. I will show how these patterns can arise in soft matter systems, charge ordered systems, neutron stars in the form of pasta phases, and in the recently proposed type-1.5 superconductors. Under application of an external drive these systems can also exhibit numerous nonequilibrium phase transitions which produce pronounced changes in the transport properties. I will also discuss how pattern formation in these systems can be influenced by a patterned substrate such as a periodic array of two dimensional pinning sites.

 

Title: Negative Magneto-Resistance in Disordered Ultra-Cold Atomic Gases
Speaker: Professor David A. W. Hutchinson
Date: 7 June 2012
Time: 4pm - 5pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Rainer Dumke
 Abstract:Anderson Localization1 was first investigated in the context of electrons in solids. One success of Anderson’s theory of weak localisation was in explaining the puzzle of negative magneto-resistance2 – as early as the 1940s it had been observed that electron diffusion rates in some materials can increase with the application of a magnetic field. This is because Anderson Localization is an interference phenomenon and breaking time reversal symmetry through the application of an external magnetic field inhibits that interference. Anderson Localization has already been demonstrated in one dimensional ultra-cold atomic gases3. We present a theoretical demonstration of weak localisation in a two-dimensional Bose condensed gas. We then demonstrate that a synthetic magnetic field can be imposed on the gas using the scheme of Spielman4. We show that this can lead to both positive and negative magneto-resistance in the gas and provide an in-depth analysis of the resulting phases.

References: [1] P. W. Anderson, Phys. Rev. 109, 1492 (1958). [2] See, for example, in P. A. Grüberg, Rev. Mod. Phys. 80, 1531 (2008) for an historical discussion of magnetoresistance in general. [3] J. Billy et al., Nature 453, 891 (2008); G. Roati et al., Nature 453, 895 (2008). [4] Y.-J. Line et al., Nature 462, 628 (2009).

 

Title: Dynamics and thermodynamics of the two-chain spin ladder: Theory and experiments in BPCB
Speaker: Professor Bruce Normand
Date: 31 May 2012
Time: 3pm - 4pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Pinaki Sengupta 
 Abstract:While many properties of the two-chain spin ladder were computed theoretically in the 1990s, experimental studies are catching up only now, because of the organometallic compound (C_5H_12N)_2CuBr_4 (BPCB). In this quasi-one-dimensional system of unfrustrated ladder units, whose energy scales match laboratory magnetic fields, it is possible to investigate quantum disordered, quantum critical, spin Luttinger-liquid, 3D magnetically ordered and fully saturated phases. This presentation reviews the range of experiments performed on BPCB, and introduces a complete bond-operator theory which describes with quantitative accuracy both thermodynamic properties and dynamical excitations at all fields and temperatures in the gapped regime. The field tuned spinon continuum in the gapless regime, seen beautifully in experiment, is described with similar accuracy at zero temperature using a Bethe-Ansatz method.

 

Title: Light trapping in thin-film solar cells: towards the Lambertian limit
Speaker: Professor Lucio Claudio Andreani
Date: 31 May 2012
Time: 3pm - 4pm 
Venue: SPMS-LT5 (SPMS-03-08)
Host: Assistant Professor Cesare Soci 
 Abstract:Solar cells based on thin-film semiconductors are very promising, but in order to increase the absorption of light in an ultra-thin semiconductor layer and to enhance the energy conversion efficiency, appropriate light-trapping schemes must be used. The maximum light trapping enhancement when the thickness of the order of the wavelength of light - and the best structures to achieve it - are still unknown. In this talk we shall review the light-trapping properties of periodic patterns etched in crystalline and amorphous silicon solar cells with anti-reflection coating and back-reflector. The results are compared with those of an unpatterned cell, and with the ultimate limits to light trapping in the case of a Lambertian (isotropic) scatterer. Photonic patterns are found to give a substantial absorption enhancement, especially for two-dimensional patterns and for thinner cells, thanks to physical mechanisms like reduction of reflection losses, diffraction of light into the cell, and coupling into the resonant optical modes of the structure. Further improvements are expected by combining ordered and disordered photonic structures.

 

Title: History of Physics: from Greeks to present day
Speaker: Professor Martial Ducloy
Date: 29 May 2012
Time: 2pm - 3pm 
Venue: SPMS - LT4 (SPMS-03-09)
Host: Associate Professor David Wilkowski
 Abstract:The history of physics does not present a smooth and continuous evolution. It will be reviewed, with a particular emphasis on the successive scientific revolutions, starting with the Miletus Ionian School in the 6th century BC, then describing the European Renaissance turn-over in the science approach, and following with the early 20th century revolutions of relativity and quantum mechanics which have paved the way to modern physics. An example of contemporary approach to scientific progress will be considered with the development of laser sources and technology.

 

Title: Recent advances in Matter-Wave Optics
Speaker: Professor Martial Ducloy
Date: 22 May 2012
Time: 4pm - 5pm 
Venue: Hilbert Space (PAP-02-02)
Host: Associate Prof. David Wilkowski
 Abstract:At the cross-over between several domains of science and technology, matter-wave optics is the field dealing with the generation and analysis of coherent matter waves. With the development of atom cooling techniques and material nanostructure fabrication, this field, as well as atom interferometry, has quickly grown. Many of the functions previously operated in light optics have been realised in atom optics: atom diffraction and reflection, beam splitters, atom holography, atom lasers, etc. The physical processes allowing one to implement those functions in matterwave optics will be reviewed, as well as their peculiar characteristics originating in the specific properties of the associated particle: non-zero mass, vacuum dispersion for the “de Broglie” wave, scalar character of the wave, internal atomic degrees of freedom, intrinsic polarisability, etc. Along this viewpoint, novel concepts in the field of matter-wave optics will be described, including atom interferometry at the nano-scale, non-diffracting atom waves and negative-index media (“metamaterials”) for matter-wave optics. Their distinct properties (atom beam profile, group velocity characteristics, wave-packet dynamics, matter-wave’s propagation…) will be analysed, comparatively to the equivalent processes in photon optics.

 

Title: Magnetism In Low Dimensions: 2D, 1D and 0D
Speaker: DR RAMESH THAMANKAR
Date: 17 May 2012
Time: 4pm - 5pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Pinaki Sengupta
 Abstract:Bulk ferromagnets Iron (Fe), cobalt (Co) and Nickel (Ni) show very complex magnetic behavior in the thin film limit. In this presentation, I will give a detailed account of magnetism in the ultra thin films of simple ferromagnets like Fe, Co and Ni and their respective alloys films. Theoretically it was perceived that bulk ferromagnets do not show long range order in the ultra thin limit (2D). But experimentally, it has been proved that magnetism exists in these low dimensions. The reason for the existence of ferromagnetism and its complex behavior in 2D and 1D is explained.

Controlling the magnetism at the nanoscale is a critical in the advancement of nanoscience and nanotechnology. In particular, arranging an array of magnetic atoms on surfaces has become very recent advancement towards information storage at the atomic scale. This also gives us a platform to study physics at the atomic level. Another fascinating advancement is usage of single molecules to perform logic operations, thus a great leap towards single molecule electronic devices. A regular array of molecules can also act as a medium for information transfer from one point to another. Thus a successful means of preparing well ordered layers of functional molecules on well defined substrates is a prerequisite for all these studies. In this talk, I will present the preparation of regular array of molecules on Cu(100) substrate. The key objective of this research is to prepare well ordered magnetic nanostructure on a well ordered organic molecular template. The molecular films are characterized using low energy electron diffraction (LEED). Scanning tunneling microscopy/spectroscopy at 20K reveals a regular array of Co dots on this network of molecules.

Reference : R. M. Thamankar, et.al, Phys. Rev. Lett. 106, 106101 (2011).

 

Title: Revolutionizing micromanipulation and sensing
Speaker: Dr Benoît Dagon
Date: 15 May 2012
Time: 10am - 11am 
Venue: Hilbert Space (PAP-02-02)
Host: Dr Alexander Petrović
 Abstract:We present miBot: an ultra compact mobile robot. It is virtually untethered and free to move, providing many advantages to manipulate and probe anything from nanoparticles, semiconductors, MEMS to biological cells. This unique solution dramatically simplifies experiment in a microscope, helping you taking your research to the next level.

 

Title: Occam's Quantum Razor: How Quantum Mechanics can reduce the complexity of Classical Models
Speaker: Dr Mile Gu
Date: 10 May 2012
Time: 4pm - 5pm 
Venue: Hilbert Space (PAP-02-02)
Host: Dr Ho Shen Yong 
 Abstract:Mathematical models are an essential component of quantitative science. They generate predictions about the future, based on information available in the present. In the spirit of Occam's razor, simpler is better; should two models make identical predictions, the one that requires less input is preferred. Yet, for almost all stochastic processes, even the provably optimal classical models waste information. The amount of input information they demand exceeds the amount of predictive information they output. Here we show how to systematically construct quantum models that break this classical bound, and that the system of minimal entropy that simulates such processes must necessarily feature quantum dynamics. This indicates that many observed phenomena could be significantly simpler than classically possible should quantum effects be involved.

Reference: Nature Communications 3, 762

 

Title: Feynman diagrams versus Fermi-gas Feynman emulator
Speaker: Professor Félix Werner
Date: 26 April 2012
Time: 4pm - 5pm 
Venue: MAS Executive Classroom 1 (MAS-03-06)
Host: Associate Professor David Wilkowski
 Abstract:Precise understanding of strongly interacting fermions, from electrons in modern materials to nuclear matter, presents a major goal in modern physics. For the first time, we sum the series of Feynman diagrams for such a many-body problem to essentially infinite order. This is made possible by a new theoretical approach, Bold Diagrammatic Monte Carlo (BDMC), which combines a Monte Carlo process capable of sampling billions of diagram topologies, bold lines representing fully dressed propagators, and divergent-series resummation techniques. Specifically, we compute the equation of state of the unitary gas – a prototypical example of a strongly correlated fermionic the equation of state of the unitary gas – a prototypical example of a strongly correlated fermionic system - in the normal unpolarised phase. We cross-validate the results with new precision experiments on ultra-cold 6Li atoms at the broad Feshbach resonance. Excellent agreement demonstrates that a series of Feynman diagrams can be controllably resummed in a nonperturbative regime using BDMC. This opens the door to the solution of challenging problems across many areas of physics.

Reference: K. Van Houcke, F. Werner, E. Kozik, N. Prokofev, B. Svistunov, M. Ku, A. Sommer, L. W. Cheuk, A. Schirotzek, M. W. Zwierlein, Nature Physics (2012), doi:10.1038/nphys2273

 

Title: Diving For Treasure In Complex Data
Speaker: Professor Marvin Weinstein
Date: 24 April 2012
Time: 4pm - 5pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Dumke Rainer
 Abstract:

“We’re drowning in data”. Navigating an ocean of high-dimensional data and searching for hidden information requires novel data-mining techniques. Dynamic Quantum Clustering, a new, unbiased, visual data-mining technology, is such a method. In this talk I will show that DQC excels at discovering and extracting unexpected structure hidden in the data without making any a-priori assumptions.

In contrast, other methods assume that clusters are topologically simple, and often assume the number of clusters that are present in the data. Our data set, containing more than half a million x-ray absorption spectra (XAS), is large and complex; yet DQC, with remarkable sensitivity, groups these spectra and identifies distinct mineralogical phases. DQC even manages to isolate an unexpected cluster (containing metallic iron and magnetite) that comprises less than 0.01 percent of the data. This bodes well for applying DQC to other complex problems in areas such as bio-informatics, physics, chemistry, epidemiology, etc.

 

Title: Multiferroics for MERAM and Geomagnetic Sensors
Speaker: Professor Nguyen Huu Duc
Date: 19 April 2012
Time: 4pm - 5pm
Venue: Hilbert Space (PAP-02-02)
Host: Professor Shen Zexiang
 Abstract:Multiferroics are materials which possess simultaneously ferromagnetic and ferroelectric properties as well as other interesting magnetoelastic phenomena. Due to the magnetoelectric coupling between these properties, the magnetization can be tuned by applying an external electrical field. This magnetoelectric (ME) effect proposed typical magnetization switching type, namely ME-induced spin reorientation. Combining the ME and GMR effect, one can develop a so-called electric-field - induced giant magnetoresistance effect. In general, this principle is called electric-field - induced magnetization switching and the corresponding memory device shall be named as magnetoelectric random access memories (MERAMs): reading by the signal of the magnetic states and writing by applying a voltage across the memory cell. The present MERAMs idea is realised with multiferroics/GMR and/or applying a voltage across the memory cell. The present MERAMs idea is realised with multiferroics/GMR and/or multiferroic-like PZT/GMR heterostructures. These are essential steps towards the fabrication of prototype MERAM elements that are reproducibly switched by the electric field. This talk also deals with the magnetic sensor using the Ni-based Meglas/PZT composite. By optimizing the 2D dimensional configuration of the laminates, a possible magnetic sensor is prepared. At low dc magnetic-fields, a ME-voltage response as high as 871 mV/Oe is achieved for the configuration with the dimension of 1×15 mm2 . This simple and low-cost fabricated sensor is promising not only for picotesla magnetic-field sensing, the azimuth and pitch angle detector but also for magnetic (reading) head applications.

 

Title: Non-equilibrium Properties of Thermally Isolated Quantum Systems
Speaker: Professor Boris Fine
Date: 16 April 2012
Time: 2pm - 3pm 
Venue: Hilbert Space (PAP-02-02)
Host: Associate Professor Christos Panagopoulos
 Abstract:Linear character of quantum mechanics poses two difficulties for the foundations of quantum statistical physics: The first difficulty is how to assign statistical weight to quantum superpositions that are not allowed classically. The second difficulty is how to deal with the notion of microscopic chaos. This talk will consist of two parts touching the above two difficulties in their respective order. The first part is to be devoted to the so-called "quantum microcanonical ensemble", where all possible quantum superpositions with a given energy expectation value are allowed. This ensemble is not equivalent to the conventional microcanonical ensemble, because the latter limits the participating eigenstates to a narrow energy window. It is to be shown that, on the one hand, the quantum microcanonical ensemble does not lead to the conventional Boltzmann-Gibbs statistics, while one the other hand, it emerges in thermally isolated clusters of spins 1/2 under multiple nonadiabatic perturbations. The second part of the talk will discuss the observable manifestations of chaos in the long-time behavior of nuclear spin decays in solids.

 

Title: BEC in External Potentials: from Condensate Deformation to Quantum Depletion
Speaker: Professor Cord Mueller
Date: 12 April 2012
Time: 4pm - 5pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Dumke Rainer
 Abstract:At low temperature, bosons condense into a many-body state where a Bose-Einstein condensate coexists with excitations. When the condensation occurs in an external potential, such as a lattice or random potential, both the condensate and its excitations show traces of the spatial confinement. As a consequence, it is in general difficult to estimate the condensate depletion caused by quantum fluctuations. Using inhomogeneous Bogoliubov theory, we calculate the one-body density matrix, as well as the momentum distribution. From there, we determine the condensate depletion analytically in weak, but otherwise arbitrary external potentials.

 

Title: Semiconductor disk lasers: a solid state dye laser technology?
Speaker: Professor Martin Dawson
Date: 27 March 2012
Time: 10.30am - 11.30am 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Sun Handong
 Abstract:Over the past few years an entirely new category of semiconductor laser has emerged to prominence: that of the semiconductor disk laser (SDL), also known as the vertical external cavity surface emitting laser (VECSEL). This hybrid technology adopts cavity design and operational principles from traditional doped-dielectric diode-pumped solid state lasers and applies them to semiconductor platelet gain media: SDLs thus combine the wavelength versatility and broad tuning associated with semiconductor band-gap engineering with the high-brightness and high intra-cavity fields typical of solid state lasers, to give ‘dye-like’ solid state lasers. The result has been a transformative technology operating from the UV to the mid infrared, offering, amongst other benefits, high powers of up to 10’s of Watts CW, low noise, tunable single frequency operation and controllable sources of GHz ultrashort pulses. Our group at the University of Strathclyde has been one of the pioneers of this exciting area and we will overview the relevant background of the technology and recent developments including using these lasers to intracavity-pump diamond (Raman) lasers.

 

Title: Surface Nanobubbles: Formation, Universality of the Contact Angle, and Stability
Speaker: Professor Detlef Lohse
Date: 22 March 2012
Time: 4pm - 5pm 
Venue: MAS Executive Classroom 1 (MAS-03-06)
Host: Associate Professor Claus-Dieter Ohl
 Abstract:We study surface nanobubbles using molecular dynamics simulation of ternary (gas, liquid, solid) systems of Lennard-Jones fluids. They form for sufficiently low gas solubility in the liquid, i.e., for large relative gas concentration. For strong enough gas-solid attraction, the surface nanobubble is sitting on a gas layer, which forms in between the liquid and the solid. This gas layer is the reason for the universality of the contact angle, which we calculate from the microscopic parameters. Under the present equilibrium conditions the nanobubbles dissolve within less of a microsecond, College of Science Nanyang Technological University SPMS-04-01, 21 Nanyang link, Singapore 637371 Fax: +65 6515 8229 Tel: +65 6513 8459 Under the present equilibrium conditions the nanobubbles dissolve within less of a microsecond, consistent with the view that the experimentally found nanobubbles are stabilized by a nonequilibrium mechanism. We interpret the experimentally found surface nanobubbles as a nonequilibrium phenomenon: Gas is pressed out of the bubble by surface tension but the outflux is compensated by an influx at the contact line. We give experimental evidence for this interpretation.
This is joint work with Joost Weijs, Jacco Snoeijer, James Seddon and Harold Zandvliet.

 

Title: Understanding complex systems: Data analysis by network approach
Speaker: Dr Won-Min Song
Date: 2 March 2012
Time: 2pm - 3pm 
Venue: MAS Executive Classroom 1 (MAS-03-06)
Host: Assistant Professor Cheong Siew Ann
 Abstract:Recently, network theory has emerged as an effective tool to model complex systems by regarding the constituents as vertices, and relevant interactions as edges. Accordingly, the importance to construct representative networks from empirical data sets, which contain meaningful information of the complex systems, has become greater. However, this task is often alluded by: (a) presence of redundancy and heterogeneity, (b) simultaneous presence of two contradicting data structures: clusters and hierarchy, and (c) lack of expertise to interpret the data. In this talk, I address these problems utilizing similarity graphs with a number of constraints, namely: Minimal Spanning Tree (MST), Planar Maximally Filtered Graph (PMFG), k nearest neighbors graph (kNN), and complete graph. I evaluate performance of these graphs to extract clusters and/or hierarchy from a data structure under presence of noises and redundancy by utilizing synthetic multivariate data sets generated with known parameters. I show that topologically constrained graphs, particularly PMFG embedded on a sphere, are suited for detecting meaningful clusters and hierarchy simultaneously. I further explore validity of graphs embedded on spheres (i.e. planar graphs) as representative networks reflecting common features of complex systems such as power-law degree distributions, clusteredness, small-worldness, and hierarchical organizations via a unique topological structure present in these graphs, called `bubble hierarchy’. Specifically, I show that, in maximal planar graphs, College of Science Nanyang Technological University SPMS-04-01, 21 Nanyang link, Singapore 637371 Fax: +65 6515 8229 Tel: +65 6513 8459 unique topological structure present in these graphs, called `bubble hierarchy’. Specifically, I show that, in maximal planar graphs, there exist a special set of subgraphs called `bubbles’ linked by separating 3-cliques, and these linking patterns of bubbles provide insights to understand disorders in complex planar networks. On the basis of these findings, I present a novel hierarchical information clustering technique called `Directed Bubble Hierarchical Tree’ (DBHT), which reveals meaningful and relevant clusters and hierarchy simultaneously and deterministically on a PMFG without any input parameters. I demonstrate the performance of DBHT technique for a range of simulated data and biological data including classification of subtypes of Diffuse Large B-Cell Lymphoma (DLBCL). I report that DBHT technique distinguishes meaningful subtypes of DLBCL automatically, which significantly differ in underlying genetic pathways/treatments. I discuss further perspectives in application of data analysis by generalizing graph-embedding techniques on hyperbolic surfaces with greater complexities than a sphere, as well as network theoretical aspects of these embedded graphs.

 

Title: Optical response of ultracold atomic systems and nanofabricated metamaterials
Speaker: Professor Harald Fritzsch
Date: 16 February 2012
Time: 4pm - 5pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Claus-Dieter Ohl
 Abstract:Today the theory of quantum chromodynamics is regarded as the correct theory of the strong interactions. In 1971 Gell-Mann and I introduced the color quantum number of the quarks, one year later the exact color symmetry group was interpreted as the gauge group of QCD. The self-coupling of the gluons leads to the property of asymptotic freedom and to the confinement of the quarks and gluons. The quarks and gluons have been observed at high energies as hadronic jets.

 

Title: Optical response of ultracold atomic systems and nanofabricated metamaterials
Speaker: Professor Janne Ruostekoski
Date: 14 February 2012
Time: 4pm - 5pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Cesare Soci
 Abstract:Ultracold atomic gases can be accurately manipulated, controlled and detected using electromagnetic fields. Such systems can respond to light cooperatively exhibiting collective optical linewidths and line shifts.
Artificially manufactured unit-cell resonators, or meta-molecules, in nanostructured metamaterial arrays share several common features with atoms in natural medium . We show how strong collective response of metamaterial systems to electromagnetic fields can be modeled by treating meta-molecules as discrete scatterers and how classical electromagnetic metamaterial response can provide analogous phenomena to quantum coherence effects in multi-level atomic systems.

 

Title: Novel magnetization phenomena in frustrated quantum magnets
Speaker: Assistant Professor Pinaki Sengupta
Date: 9 February 2012
Time: 4pm - 5pm 
Venue: Hilbert Space (PAP-02-02)
Host:  
 Abstract:Geometrically frustrated spin systems are known to exhibit novel quantum phenomena. One example is the unique nonmonotonic field dependence of the magnetization and the associated emergence of magnetization plateaus in a class of frustrated spin compounds commonly known as the ShastrySutherland compounds after their underlying magnetic lattice. In this talk, I shall discuss the underlying mechanism for the formation of these plateaus.

 

Title: Imaging in multiple scattering media
Speaker: Emeritus Professor Roger Maynard
Date: 2 February 2012
Time: 4pm - 5pm 
Venue: Hilbert Space (PAP-02-02)
Host: Associate Professor David Wilkowski
 Abstract:Multiple scattering of waves in disordered media is very frequent and biquitous in nature, ranging from the solar light propagation in clouds to cold atoms and seismic waves in the terrestrial crust. All these different waves can be multiply scattered by the homogeneities of the medium where they propagate (water droplets, atoms, defects and cracks, etc). Recent studies on the problem of wave propagation in complex systems have led to an unified picture where novel interference effects (like the coherent backscattering phenomenon) and long-range space and time correlations have been discovered, leading to new techniques like diffuse wave spectroscopy. All these recent advances are at the origin of new imaging methods in diffuse medium. The challenge to reach the shortest resolution for imaging, the so-called Rayleigh limit of half the wavelength, can be accomplished in diffuse media by using cross-correlations of fluctuations due to ambient noise at two distant points (passive imaging), together with a time reversal mirror and phase monitoring.

 

Title: Graphene: Revisiting old questions in a new material
Speaker: Dr Shaffique Adam
Date: 13 January 2012
Time: 2pm - 3pm
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Yu Ting 
 Abstract:From the hard-drives that harness giant magneto-resistance to the transistors that drive modern processors, solid state physics is at the very heart of the technological revolution. Implied in this effort is a thorough understanding of electronic systems in nanoscale geometries. In this context, the complex interplay between disorder, electron-electron interactions and quantum interference is an interesting backdrop to many of the unsolved mysteries in condensed matter physics. About five years ago, a new electronic material appeared – notable not only for its ease of preparation and theoretical simplicity, but also by its promise for future electronic devices [1]. Single monatomic sheets of carbon, known as graphene, have an electronic dispersion that is reminiscent of light, in that they can be described as a massless Dirac particle. In many ways, graphene is a textbook system to test physical models – for instance, similar to field-effect transistors, the electron density in grapheme sheets can be modulated by a backgate. However, unlike conventional semiconductors, the carrier density can be continuously tuned from electronlike carriers for large positive gate bias to hole-like carriers for negative bias, with the Dirac point defined as the singularity that marks the transition from electrons to holes. When graphene is close to charge neutrality, its energy landscape becomes highly inhomogeneous, forming a sea of electron-like and hole-like puddles, which determine the properties of graphene at low carrier density. In this talk, I will discuss how the electronic properties of the Dirac point provide an intriguing example of how the competing effects of disorder, electron-electron interactions, and quantum interference conspire together to give a surprisingly robust state whose properties can be described using semi-classical methods. Armed with this success, I will discuss how future graphene experiments could shed light on some long-standing open questions in condensed matter physics.

References
[1] S. Das Sarma, S. Adam, E. H. Hwang, E. Rossi, “Electronic transport in two dimensional graphene”, Rev. Mod. Phys. 83, 407 (2011).

 

Title: Information and the quantum
Speaker: Dr Tomasz Paterek
Date: 11 January 2012
Time: 10am - 11am 
Venue: Hilbert Space (PAP-02-02)
Host: Associate Professor Phan Anh Tuan
 Abstract:In this talk two approaches shall be presented that aim at understanding foundations of quantum theory. Both of them are in the spirit of Wheeler's "it from bit" and obtain certain quantum features without involving quantum formalism. We first derive the strength of quantum correlations from the principle of information causality. It captures the fact that information is always encoded in physical systems and it is impossible for a receiver to retrieve data that was not encoded by the sender. Trivial as it sounds, it is perhaps even more surprising that information causality has nontrivial consequences. Next we partially answer the question about the origin of random outcomes in quantum experiments. It will be shown that randomness occurs due to limited information content of a physical system that is "asked" in a measurement about data which cannot be derived from the information stored in the system. In this approach quantum randomness is a manifestation of logical independence.

 

Title: Nanomaterials and Nanostructures for Electronics and Photonics
Speaker: Dr Zhiyong Fan
Date: 10 January 2012
Time: 3.30pm - 4.30pm
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Fan Hongjin
 Abstract:Materials made of nano/micro-structures have unique physical properties, such as fast carrier transport, high surface-to-volume ratio, mechanical flexibility, sub-wavelength optical waveguiding, etc. These intriguing properties can be harnessed for a variety of applications in electronics and photonics. In the past, we have fabricated an assortment of semiconductor nanowires, including Si, Ge, CdSe, InAs, ZnO, etc. We have performed systematic investigations on electronic and optoelectronic properties of these materials by configuring them as transistors, photodiodes and sensors. More importantly, we have developed scalable processes to integrate semiconductor nanowires into ordered arrays for large scale electronic applications. Utilizing these approaches, we have fabricated all-nanowire based high frequency devices and integrated circuits with functionality. In the meantime, we have developed several self-organized approaches to fabricate three-dimensional (3-D) nanostructures. These 3-D structures have demonstrated geometry dependent photon management property thus have promising potential for photonic applications. In particular, we have fabricated 3-D nanopillar arrays, nanospike arrays and nanowell arrays. Optical absorption properties of these nano-engineered structures have been investigated with experimental methods as well as theoretical simulations. To explore their photonic applications, nanopillar and nanospike arrays have been fabricated into photovoltaic devices; preliminary results have shown that they can demonstrate improved performance as compared to planar control samples, indicating their potency for cost-effective solar cells.

 

Title: Quantum Control of Light and Matter
Speaker: Professor Jaewook Ahn
Date: 9 January 2012
Time: 3.30pm - 4.30pm
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Elbert Chia 
 Abstract:Recent advances in ultrafast laser and optical pulse shaping techniques have brought the use of shaped pulses of optical frequency for the manipulation of quantum systems. This field, known as quantum control, though being started as a theoretical exercise, has rapidly become an experimental reality in a vast variety of materials extending from atoms and molecules to condensed matter and biological materials. In this talk, after reviewing the key concepts in quantum control, we present our latest experiment of quantum control of cold atoms.

 

Title: Nanofiber Quantum Electrodynamics
Speaker: Dr Fam Le Kien
Date: 9 January 2012
Time: 2pm to 3pm 
Venue: Hilbert Space (PAP-02-02)
Host: Associate Professor Phan Anh Tuan
 Abstract: Coupling of light to subwavelength structures and its control pose one of the greatest challenges of recent research. A nanofiber is a subwavelength-diameter fiber, with a vacuum clad and a silica core. Nanofibers with diameters down to 50 nm have been produced. A nanofiber can tightly confine the field in an area comparable to the light wavelength. It is known that optical cavities can increase the interaction between atoms and photons. It is natural to expect that the use of a nanofiber can substantially enhance the interaction between atoms and guided-mode photons.

In this talk, I present the recent research results of our group on quantum electrodynamics with nanofibers. I describe the specific structure of the guided modes of nanofibers, the efficient channeling of emission from an atom into a nanofiber, and the enhancement of channeling efficiency due to the collective effect or the use of a cavity. I also discuss the triggered generation of single guided photons and entangled guided photons.