Dr. Xiao Li joined City University of Hong Kong as an Assistant Professor in January 2019. Previously he worked as a postdoc associate in the Condensed Matter Theory Center, University of Maryland (College Park) from 2015 to 2018. Dr. Li received his BSc degree from Peking University in 2008 and his PhD degree in Physics from The University of Texas at Austin in 2014. Dr. Li is generally interested in exotic quantum phases that arise from the interplay between topology, disorder, and many-body interactions. Recently, his research focus has been on many-body localization and nonergodic phases of matter. Dr. Li has published 27 high-quality papers, including seven in Physical Review Letters, one in Nature Communications, and one in Nature.
In this talk, I will discuss our recent work on many-body localization (MBL) for interacting one-dimensional lattice fermions in random (Anderson) and quasiperiodic (Aubry-Andre) models, focusing on the role of interaction range. We obtain the MBL quantum phase diagrams by calculating the experimentally relevant inverse participation ratio (IPR) at half-filling using exact diagonalization methods and extrapolating to the infinite system size. For short-range interactions, our results produce in the phase diagram a qualitative symmetry between weak and strong interaction limits. For long-range interactions, no such symmetry exists as the strongly interacting system is always many-body localized, independent of the effective disorder strength, and the system is analogous to a pinned Wigner crystal. We obtain various scaling exponents for the IPR, suggesting conditions for different MBL regimes arising from interaction effects.