News & Events

Speaker: Ying-Cheng Lai
Affiliation: Arizona State University, USA & University of Aberdeen, UK
Abstract Details: Quantum chaos is referred to the study of quantum manifestations of systems that are chaotic in the classical limit. Most previous research in the field of quantum chaos focused on the non-relativistic quantum regime. Recently the field of relativistic quantum chaos has emerged, due to the tremendous development of research on graphene. Phenomena such as relativistic quantum scarring, chaotic scattering, and tunneling have been explored. The speaker will discuss a number of fundamental issues in relativistic quantum chaos, but from the perspective of quantum control or modulation: how classical chaos can be exploited to harness relativistic quantum behaviors in Dirac fermion and graphene systems? Transport through quantum dot and resonant tunneling will be used as two prototypical examples to illustrate the principle that chaos-based quantum control can be advantageous and experimentally feasible.
About the Speaker: Ying-Cheng Lai is a Professor of Electrical Engineering and Physics at Arizona State University, USA and the Sixth-Century Chair in Electrical Engineering at University of Aberdeen, UK. His research areas are complex systems, quantum chaos, graphene physics, nonlinear dynamics in optomechanical systems, mathematical biology, signal processing and data analysis. His current H-index is 52 and i10-index is 210. He is a frequent visitor to NUS' Physics Department.
Click HERE for directions

—
To view all the upcoming seminars, you can visit: https://graphene.nus.edu.sg/news-events/events/
You may also Like & Subscribe our following channels below to receive instant notifications for new announcements.

Speaker: Enrique del Barco
Affiliation: Physics Department, U. Central Florida, USA
Abstract Details: Electrical transport properties of individual molecules have received considerable attention over the last several years due to the introduction of single-electron transistor (SET) devices. The potential of single-electron transport spectroscopy for the understanding of the fundamental physics and chemistry of individual molecules has been recently demonstrated by various breakthrough experimental discoveries. For example, transport excitations associated with fundamental vibrational modes of an individual C60 molecule in a SET have been reported. More recently, groups at Cornell and Harvard have observed the Kondo effect in individual paramagnetic molecules. Along these lines, single-molecule magnets (SMMs) will provide a unique venue for probing novel aspects of the interplay between conduction electrons and molecular spin levels. I will discuss some of the phenomena expected to be observed in the conductance through a SMM-based SET. I will also describe the fabrication procedure and characterization of three terminal single-electron transistor devices utilizing Al/Al2O3 gate electrodes developed for these studies. The devices are patterned via multiple layers of optical and electron beam lithography. Electromigration induced breaking of the nanowires reliably produces 1-3 nm gaps in between which the SMM is sandwiched. Preliminary results of the conductance through a Mn4 SMM displaying the coulomb blockade effect with several excitations that bend with the magnetic field have already been obtained.
Click HERE for directions

—
To view all the upcoming seminars, you can visit: https://graphene.nus.edu.sg/news-events/events/
You may also Like & Subscribe our following channels below to receive instant notifications for new announcements.

Speaker: Andreas Schnyder
Affiliation: Max Planck Institute, Stuttgart
Abstract Details: Noncentrosymmetric superconductors (NCSs) are important candidates for realizing topological superconducting phases, with either a full or a nodal bulk gap. The topology of nodal phases is manifested by the presence of nondegenerate 'flat-band'' zero-energy surface states, in contrast to the dispersing modes characteristic of fully gapped topological superconductors. In both cases, the edge states are expected to possess an intricate spin structure. This observation suggests that signatures of the bulk topology may be found in the magnetic response of the surface. In this talk, I demonstrate that a charge current develops in an NCS close to its interface with a ferromagnet (FM). The current is dominated by the response of the topologically protected edge states of the NCS to the FM's exchange field, and hence has completely different characteristics for the fully gapped and nodal NCS. For example, while the current in the fully gapped NCS is weak and saturates to its zero-temperature value, the presence of nondegenerate flat bands in the nodal NCS is responsible for an enormous enhancement of the current at low temperatures. This provides a novel test of the topology of NCSs, in particular of the existence of nondegenerate flat-band states. More generally, we have shown the promise of exploiting the spin texture of surface states to reveal the topological properties of the bulk.
Click HERE for directions

—
To view all the upcoming seminars, you can visit: https://graphene.nus.edu.sg/news-events/events/
You may also Like & Subscribe our following channels below to receive instant notifications for new announcements.

Speaker: Predrag Lazic
Affiliation: Rudjer Boskovic Institute, Zagreb, Croatia
Abstract Details: Experimental and theoretical study of Cs and Eu atoms adsorption on graphene on Ir(111) will be presented. Graphene on Ir(111) surface is an interesting system because graphene has almost pristine electronic structure in it due to its weak bonding character to Iridum surface. The bonding is almost exclusively of the van der Waals type. However adding Cs or Eu atoms graphene gets doped and and nature of binding changes - especially in the case when the atoms intercalate. Density Functional Theory calculations with standard semilocal functionals (GGA) -- fail to reproduce experimental findings even qualitatively. Only when the newly developed nonlocal correlation functional is used (vdW-DF) which includes van der Waals interactions, are the calculations in agreement with experiment, revelaing the mechanism of graphene delamination and relamination which is crucial for intercalation and trapping of atoms under the graphene.
About the Speaker: Predrag Lazic received his Ph.D. in theoretical physics - condensed matter from the University of Zagreb in 2007. As a Humboldt scholar in Forschungszentrum Juelich (Germany) he continued working on surface physics, particularly on spin transport through molecules on surfaces. During that time, he pioneered the implementations of van-der-Waals interactions within the DFT methods. In the following years, he joined Ceder group at Massachusetts Institute of Technology (USA), where he worked on predicative theory for water-splitting catalytic materials. In June 2012, he joined the Rudjer Boskovic Institute (Croatia) as a research scientist . His current research interests include surface science and material science, with particular interest in graphene, spintronics and surface catalysis for energy applications. In his spare time, he developed a novel 'Robin Hood' numerical method for fast solving boundary value problems, and commercialised it through his company Artes Calculi (http://www.artcalc.com/). He has published more than 40 journal papers.
Click HERE for directions

—
To view all the upcoming seminars, you can visit: https://graphene.nus.edu.sg/news-events/events/
You may also Like & Subscribe our following channels below to receive instant notifications for new announcements.

Speaker: Song-Lin Li
Affiliation: National Institute for Materials Science, Japan
Abstract Details: Two-Dimensional Materials for Next-Generation Nanoelectronics: New Structures and Device Physics Two-dimensional layered materials including graphene and molybdenum disulfide (MoS2) have received great attention in atomic field-effect transistor (FET) technology and post-silicon electronics because of their unique atomic-scale thickness and flatness. However, numerous physical and technological issues have to be addressed before practical use. In this talk, we will summarize our efforts in this research filed. The talk consists of two parts: 1) new structures for graphene logic gates and 2) device physics for MoS2 FETs. In the first part, we will introduce the formation of elementary graphene logic gates with a self-adaptive complementary-like architecture, in which the ambipolar nature is used as a benefit rather than a drawback to form logic devices. High-performance voltage inverters with voltage gain large than unity are achieved by using a highly efficient gating technique.[1] The voltage gain can be further enhanced when bilayer graphene is adopted as channel and an energy gap is introduced by perpendicular electric fields.[2] Complementary-like logic NAND and NOR gates are also demonstrated.[3] Physical issues on thickness characterization, carrier injection and scattering mechanisms for MoS2 atomic layers will be addressed in the second part. A rapid and nondestructive layer counting technique for the atomic MoS2 layers is developed by using interference Raman spectroscopy.[4] The carrier injection from metal electrode to ultrathin MoS2 layers is found to be easier than corresponding bulk structures due to lowered effective injection barriers and distinct emission mechanism. Finally, the channel thickness dependent carrier mobility and related carrier scattering mechanism in atomic FETs will be elaborated.[5] References [1] S.-L. Li et al, Nano Lett. 2010, 10, 2357; [2] S.-L. Li et al, ACS Nano 2011, 5, 500; [3] S.-L. Li et al, Small 2011, 7, 1552; [4] S.-L. Li et al, ACS Nano 2012, 6, 7381; [5] S.-L. Li et al, submitted.
About the Speaker: Dr. Li received his Ph.D. degree in Condensed Matter Physics in 2009 at the Institute of Physics, Chinese Academy of Sciences, China, where he worked on superconductivity and resistance switching effect in oxide thin films. Afterwards, he moved to the National Institute for Materials Science, Japan for his postdoctoral research. He was a research associate during August, 2009 to September, 2011, and was promoted to ICYS-MANA researcher at the International Center for Young Scientist. Now he focuses on the device physics and electronics in two-dimensional materials."
Click HERE for directions

—
To view all the upcoming seminars, you can visit: https://graphene.nus.edu.sg/news-events/events/
You may also Like & Subscribe our following channels below to receive instant notifications for new announcements.

Speaker: Nian X. Sun
Affiliation: Northeastern University, USA
Abstract Details: The coexistence of electric polarization and magnetization in multiferroic materials provides great opportunities for realizing magnetoelectric coupling, including electric field control of magnetism, or vice versa, through a strain mediated magnetoelectric interaction effect in layered magnetic/ferroelectric multiferroic heterostructures. Strong magnetoelectric coupling has been the enabling factor for different multiferroic devices, which however has been elusive, particularly at RF/microwave frequencies. In this presentation, I will cover the most recent progress on novel layered microwave multiferroic heterostructures and devices, which exhibit strong magnetoelectric coupling. We will demonstrate strong magnetoelectric coupling in novel microwave multiferroic heterostructures. These multiferroic heterostructures exhibit a giant voltage tunable magnetic field of 3500 Oe, and a high electrostatically tunable ferromagnetic resonance frequency range between 1.75~ 7.57 GHz, a tunable frequency of 5.82 GHz or fmax/fmin=4.3. At the same time, we will demonstrate E-field modulation of anisotropic magnetoresistance, giant magnetoresistance and exchange bias at room temperature in different multiferroic heterostructures. New multiferroic devices will also be covered in the talk, including ultra-sensitive nanoelectromechanical systems magnetoelectric sensors with picoTesla sensitivity, multiferroic voltage tunable bandpass filters, voltage tunable inductors, tunable bandstop filters, tunable phase shifters and spintronics.
About the Speaker: Nian Sun is an associate professor at the Electrical and Computer Engineering Department, Northeastern University. He is on sabbatical leave as a visiting scientist at MIT. He received his Ph.D. degree from Stanford University. Prior to joining Northeastern University, he was a scientist at IBM and Hitachi Global Storage Technologies. Dr. Sun was the recipient of the NSF CAREER Award, ONR Young Investigator Award, the Søren Buus Outstanding Research Award, etc. His research interests include novel magnetic, ferroelectric and multiferroic materials, devices and subsystems. He has over 120 publications and has >20 patents and patent disclosures. One of his papers was selected as the “ten most outstanding full papers in the past decade (2001~2010) in Advanced Functional Materials”. Dr. Sun has given over 60 invited or keynote presentations in national and international conferences and universities. He is an editor of IEEE Transactions on Magnetics, and a fellow of the Institute of Physics and of the Institution of Engineering and Technology.

Click HERE for directions

—
To view all the upcoming seminars, you can visit: https://graphene.nus.edu.sg/news-events/events/
You may also Like & Subscribe our following channels below to receive instant notifications for new announcements.

Speaker: Bogdan A. Bernevig
Affiliation: Department of Physics, Princeton University, USA
Abstract Details: A complete classification of non-interacting topological insulators with time-reversal and charge conjugation symmetry is known. It contains many cases in which no topological class can be defined - for example classes with spineless time-reversal symmetry. We show that the introduction of point-group symmetry provides a grading which gives rise to many new topological classes which are outside the regular table of topological insulators. Simple examples are topological insulators stabilized by rotational C_n and spineless time-reversal symmetry. We provide a classification of such crystalline topological states and analyze their possible appearance in electronic systems and photonics crystals.
Click HERE for directions

—
To view all the upcoming seminars, you can visit: https://graphene.nus.edu.sg/news-events/events/
You may also Like & Subscribe our following channels below to receive instant notifications for new announcements.

Speaker: Mirco Milletari
Affiliation: NUS Physics and Graphene Centre
Abstract Details: We investigate the effect of non-equilibrium and interactions on shot noise in u=2 quantum Hall edges [1], where interactions between the two co-propagating edge modes are expected to give rise to charge fractionalization. We consider a setup consisting of a Hall bar pinched by two Quantum point contacts (QPCs). The first QPC selectively drives out of equilibrium the outer edge mode only, which then interacts with the unbiased inner one over the distance between the two QPCs. We describe the edge modes by two chiral Luttinger liquids, whose coupling is introduced via a quantum quench [2, 3]. In order to study the relaxation dynamics of the inner edge mode, we employ the method of non-equilibrium bosonization [4]. Non-equilibrium bosonization is a convenient framework to treat exactly strongly interacting, one dimensional systems far from equilibrium. The core feature of this method is the relation between the observables of the theory and the determinants of full counting statistics. Contrary to some claims in the literature, true fractionalization is only possible when the two edge modes are out of equilibrium. At equilibrium there would be zero measured noise in edge mode 2 after QPC2. We carefully consider this issue by carefully taking into account the joint effects of interactions and non-equilibrium. In our model, we find that even asymptotically the edge distribution function does not thermalize, but instead depends in a sensitive way on the interaction strength between the two edge modes. We compute shot noise and Fano factor from the asymptotic distribution function of the inner edge mode at the second QPC, and from comparison with a reference model of fractionalized excitations we find that the Fano factor can be close to the value of the fractionalized charge. [1] M. Milletari B. Rosenow, eprint arXiv:1207.1719, (2012) [2] A.Iucci, M.A. Cazalilla, Phys. Rev. A 80, 063619 (2009) [3] D.L. Kovrizhin, J.T. Chalker, Phys. Rev. B 84, 085105 (2011) [4] D. B. Gutman, Y. Gefen, A.D. Mirlin, Phys. Rev. B 81, 085436 (2010)
Click HERE for directions

—
To view all the upcoming seminars, you can visit: https://graphene.nus.edu.sg/news-events/events/
You may also Like & Subscribe our following channels below to receive instant notifications for new announcements.

Speaker: Kush Saha
Affiliation: IACS Kolkata, India
Abstract Details: After a brief introduction of the ideas of experimental generation of synthetic gauge fields, I shall talk about the physics of interacting bosons in their presence. In particular, I shall discuss superfluid-Mott insulator (SI) transitions in a two dimensional square lattice at commensurate filling and in the presence of a synthetic periodic vector potential characterized by tunable strength p and period q. I shall then show the p and q dependence of the momentum distribution of the bosons in the Mott phases near the SI transitions and demonstrate that the bosons exhibit several reentrant field-induced SI transitions for any fixed period q. Finally I will comment on the superfluid density of the resultant superfluid state near such a SI transition.
Click HERE for directions

—
To view all the upcoming seminars, you can visit: https://graphene.nus.edu.sg/news-events/events/
You may also Like & Subscribe our following channels below to receive instant notifications for new announcements.

Speaker: Jeil Jung
Affiliation: Graphene Centre, NUS
Click HERE for directions

—
To view all the upcoming seminars, you can visit: https://graphene.nus.edu.sg/news-events/events/
You may also Like & Subscribe our following channels below to receive instant notifications for new announcements.