YONG Ee Hou portrait
Asst. Prof.

Division of Physics and Applied Physics, SPMS, Nanyang Technological University
Plenary 1: The Geometry and Shape of Nature
28 Sept, 9:45am

The study of forms and patterns in nature is a fascinating one that goes back to antiquity and really evolved into a formal discipline after the pioneering work of D’Arcy Thompson, whose century-old classic “On growth and form” is still in print! Since then, there has been an increasing appreciation of the role in which geometry, elasticity, and topology play in the morphology of things. In this talk, I will present my foray into this wonderful world, and try to bridge perspectives from morphology, ecology, evolution, and development.

[1] E. H. Yong, F. Dary, L. Giomi, and L. Mahadevan: Statistics and topology of fluctuating ribbons, Proc. Natl. Acad. Sci. 119 (32), e2122907119 (2022).
[2] M. C. Stoddard, E. H. Yong, D. Akkaynak, C. Sheard, J. Tobias, and L. Mahadevan: Form, Function and Evolution of Avian Egg Shape, Science 356, 1249–1254(2017).

Denis Bandurin picture
Asst. Prof.
Denis Bandurin

Department of Materials Science and Engineering,
National University of Singapore
Plenary 2: Light-matter interaction in the flatland: recent advances and novel applications
28 Sept, 10:15am

Since the first isolation of graphene, devices based on novel low-dimensional materials (LDM) and their heterostructures have become a gold mine for exploring new fundamental phenomena. Reduced dimensionality, peculiar band structures, quantum geometry, and strong quasiparticle interactions in a unique way determine the response of LDM to external fields thereby offering a powerful setting by which to probe novel radiation-matter interaction effects and prototype future optoelectronic technology. In the first (fundamental) part of my talk, we will discuss light-matter interaction effects arising in LDM due to the excitation of plasmons. I will present our recent results on the quasi-relativistic Fizeau drag effect [1]. Predicted by Fresnel in the XIX century and demonstrated by Fizeau, dragging of light by the flow of water was among the cornerstones of Einstein's special relativity. Our experiments on graphene materialized the electronic version of this fundamental effect in which the flow of electrons on par with the moving medium was found to alter the surface plasmon polaritons (SPP) dispersion (Fig. 1). The importance of the observed plasmonic Fizeau drag is that it enables breaking of time-reversal symmetry and reciprocity at infrared frequencies without resorting to magnetic fields or chiral optical pumping. Next, we will discuss peculiar effects arising in graphene plasmonics when the latter is subjected to a perpendicular magnetic field. I will show that graphene supports the propagation of slow Bernstein collective modes whose diverging density of plasmonic states results in strong magnetoabsorption at THz frequencies [2]. In the second (applied) part of my talk, I will show that with a proper processing, atomically thin high-temperature cuprate superconductors can be used in single-photon detection technology. We will discusshow to fabricate superconducting nanowires out of thin flakes of Bi2Sr2CaCu2O8+δ (BSCCO) and La1.55Sr0.45CuO4/La2CuO4 (LSCO-LCO) bilayer films and then, look at their response to visible and infrared light. I will show, that both materials feature single-photon operation above liquid helium temperature as revealed through the linear scaling of the photon count rate on the radiation power. For the BSCCO detectors, we observed single-photon sensitivity at the technologically important 1.5 μm telecommunications wavelength up to 25 K [3].

Fizeau drag figure

Fig. 1. Fizeau drag in graphene plasmonics. a, Schematic of a graphene device with a constricted channel. Under the illumination of an infrared laser, the gold launcher excites propagating SPPs, which were visualized by near-field tip-based imaging techniques. Black streamlines represent carrier drift directions. b, SPP line profiles without d.c. current (black) and with Jdc = 0.69 mA μm−1 (blue), illustrating a reduction of the SPP wavelength.

[1] Dong, Y., Xiong, L., Phinney, I.Y., Sun, Z., Jing, R., McLeod, A.S., Zhang, S., Liu, S., Ruta, F.L., Gao, H., Dong, Z., Pan, R., Edgar, J.H., Jarillo-Herrero, P., Levitov, L.S., Millis, A.J., Fogler, M.M., Bandurin, D.A., Basov, D.N.: Fizeau drag in graphene plasmonics. Nature 594, 513–516 (2021).
[2] Bandurin, D.A., Mönch, E., Kapralov, K., Phinney, I.Y., Lindner, K., Liu, S., Edgar, J.H., Dmitriev, I.A., Jarillo-Herrero, P., Svintsov, D., Ganichev, S.D.: Cyclotron resonance overtones and near-field magnetoabsorption via terahertz Bernstein modes in graphene. Nat. Phys. 18, 462–467 (2022).
[3] Charaev, I., Bandurin, D.A., Bollinger, A.T., Phinney, I.Y., Drozdov, I., Colangelo, M., Butters, B.A., Taniguchi, T., Watanabe, K., He, X., Božović, I., Jarillo-Herrero, P., Berggren, K.K., Single-photon detection using high-temperature superconductors. arXiv:2208.05674v1 (2022).

Bent Weber portrait
Asst. Prof.
Bent Weber

School of Physical and Mathematical Sciences,
Nanyang Technological University
Plenary 3: Many-body Interactions and Induced Superconductivity in a 2D Topological Insulator
28 Sept, 11:00am
The interplay of topology, superconductivity, and many-body correlations has become a subject of intense research for the pursuit of non-trivial superconducting pairing. The boundaries of atomically-thin 2D topological insulators – amongst them the quantum spin Hall (QSH) insulator [1] – provide a natural realization of strictly 1D electronic structure with linear dispersion and spin-momentum locking (helicity), in which electronic interactions have been predicted to give rise to a low-temperature correlated ground state. As one of the most promising materials realizations of the quantum spin Hall state, we show that atomic monolayers of the transition metal dichalcogenide 1T’-WTe2 provide a unique testbed for the 1D helical states, and towards non-trivial superconducting pairing therein [2].
[1] M.S. Lodge, S.A. Yang, S. Mukherjee, and Bent Weber*: Atomically Thin Quantum Spin Hall Insulators. Advanced Materials 33, 2008029 (2021).
[2] W. Tao, Z.J. Tong, A. Das, D.-Q. Ho, Y. Sato, M. Haze, J. Jia, Y. Que, F. Bussolotti, K.E.J. Goh, B. Wang, H. Lin, A. Bansil, S. Mukherjee, Y. Hasegawa, and Bent Weber*: Multiband super-conductivity in strongly hybridized 1T′-WTe2 / NbSe2heterostructures. Physical Review B 105, 094512 (2022).

Alvin Chua portrait
Asst. Prof.
Alvin CHUA

Department of Physics,
National University of Singapore
Plenary 4: Observing gravitational-wave sources with space-based detectors
30 Sept, 9:00am

Seven years on from LIGO's first detection of gravitational waves (GWs), astrophysical GW sources are now routinely observed by a growing network of ground-based detectors at both high and low frequencies. In the next decade, space interferometers such as the LISA mission will probe the mid-frequency GW band, where the richest population of sources radiate. My talk today will include a broad update on the present status of ground-based observing, followed by a brief introduction to the distinctive challenges of space-based GW astronomy. I will also discuss how modern computational and statistical techniques are being brought to bear on a variety of open problems in LISA scientific analysis.

Chelsea Sharon portrait
Asst. Prof.
Chelsea SHARON

YaleNUS College
Plenary 5: Molecular Gas Diagnostics of AGN Feedback
30 Sept, 9:30am

Theoretical work has suggested that active galactic nuclei (AGN) play an important role in quenching star formation in massive galaxies. However, direct observational evidence of AGN affecting molecular gas (the fuel for star formation) via outflows is challenging to obtain, particularly at high redshift when cosmic star formation rates were at their highest. Indirect evidence for AGNs’ impact on their host galaxies’ cold gas phase may be provided by measurements of the gas excitation. I will present recent observations of high-excitation CO lines from the Atacama Large Millimeter/submillimeter Array for a small sample of z≈2-6 purely star-forming galaxies and known AGN host galaxies. We find that the CO spectral line energy distributions are somewhat heterogenous, even at high excitation. We will discuss why these objects may have produced such mixed results, and how other observables, such as line widths, may add clarity to the gas heating mechanisms.

Ho Wen Wei portrait
Asst. Prof.
HO Wen Wei

Department of Physics,
National University of Singapore.
Plenary 6: Many-body physics and quantum information science in the age of noisy, intermediate-scale quantum (NISQ) devices
30 Sept, 10:00am

There is currently a tremendous global effort invested into building quantum computing technologies. While today's devices are still far from having the fault-tolerance required to perform reliable large-scale computation, they are nevertheless exceptional platforms ideal for the investigation of quantum many-body physics in regimes that go beyond conventional material experiments. This stems from their unprecedented capabilities for control and measurement. In this talk I will demonstrate how such capabilities allow for the probing of a novel phenomenon in dynamics, namely a deeper form of quantum thermalization (the process by which systems settle down over time), in which not just local observables relax to universal values but also conditional post-measurement wave-functions acquire a universally random distribution. Quantum information theoretic concepts are used to characterize this, showing the importance of the union of many-body and quantum information frameworks to yield new insights into fundamental phenomena. Time-permitting, I will sketch how such universal randomness can in fact be used as a resource for applications in quantum information science, like quantum state learning.