FLEET Seminar: Yuerui Larry Lu – Enhanced Interactions of Interlayer Excitons in Free-standing Hetero-bilayers

Prof. Yuerui (Larry) Lu, School of Engineering, Australian National University (ANU)

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Abstract

Strong, long-range dipole-dipole interactions between interlayer excitons (IXs) can lead to novel multi-particle correlation regimes that drive the system into distinct quantum and classical phases including dipolar liquids, crystals, and superfluids. Both repulsive and attractive dipole-dipole interactions have been theoretically predicted between IXs in a semiconductor bilayer, but only repulsive interactions have been experimentally reported so far. We investigated free-standing, twisted (51^o, 53^o, 45^o), tungsten diselenide/tungsten disulfide (WSe₂/WS₂) hetero-bilayers, where we observed a transition in the nature of dipolar interactions among IXs from repulsive to attractive [Nature 610, 478–484 (2022)]. This was caused by quantum-exchange-correlation effects, leading to the appearance of a robust interlayer biexciton (formed by two IXs) phase that was theoretically predicted but never observed in experiments before. The reduced dielectric screening in a free-standing hetero-bilayer not only resulted in a much higher formation efficiency of IXs, but also led to strongly enhanced dipole-dipole interactions, which allowed us to observe the many-body correlations of pristine IXs at the two-dimensional (2D) quantum limit. Our findings can open avenues for exploring new quantum phases with potential for application in nonlinear optics.

About the speaker

Prof. Yuerui (Larry) Lu is a professor in School of Engineering at the Australian National University (ANU). He received his Ph.D. degree from Cornell University in 2012, and B.S. degree from University of Science and Technology of China. His research interests include 2D quantum materials and optoelectronic devices, MEMS sensors and actuators, biomedical novel devices, etc. He has published 2 books (as editor), 7 book chapters, and more than 100 papers in high-impact journals, including Nature, Science, Nature Physics, Nature Communications, Light: Science & Applications, etc. He was the recipient of several competitive awards, including the Investigator Award from National Health and Medical Research Council (NHMRC) in 2022, Young Innovator Award from Springer Publishing Group in 2020, Future Leader Fellowship and Paul Korner Innovation Award from National Heart Foundation of Australia in 2019, Outstanding Supervisor Award for 3MT (3 minutes thesis) Competition from ANU in 2018, ACT Young Tall Poppy of 2016, Media and Outreach Award from ANU in 2015, Discovery Early Career Research Award (DECRA) from Australian Research Council (ARC) in 2014, Future Engineering Research Leadership Fellow from ANU in 2013.