October: Xiaoyu Wang

Theory of correlated Chern insulators in twisted bilayer graphene

Xiaoyu Wang

National High Magnetic Field Lab

Wednesday, October 18

2:00 pm ET/11:00 am PT

Abstract:

Magic-angle twisted bilayer graphene is the best studied physical platform featuring moire potential induced narrow bands with non-trivial topology and strong electronic correlations. Despite their significance, the Chern insulating states observed at a finite magnetic field -- and extrapolating to a band filling, s, at zero field -- remain poorly understood. Here we report the first comprehensive study of interacting electrons in finite magnetic fields while varying the electron density, twist angle and heterostrain. Within a panoply of correlated Chern phases emerging at a range of twist angles, we uncover a unified description for the ubiquitous sequence of states with Chern number t for (s,t)=\pm (0,4), \pm(1,3),\pm(2,2) and \pm(3,1).  In addition, we find correlated Chern insulators at unconventional sequences with fractional s, and elucidate their nature. 

Bio:

Xiaoyu Wang is a visiting research faculty member at the National High Magnetic Field Lab in Tallahassee, FL. His research interest is on theoretical studies of correlated and topological electronic systems, including cuprate and iron pnictide superconductors, 2D moiré electronic materials, topological Kondo insulators etc. His expertise is in many body techniques as well as numerical methods such as Quantum Monte Carlo and self-consistent Hartree-Fock. Prior to the current position, he was a Moore postdoc at MagLab from 2022-2023, a Dirac fellow from 2019-2022, and a postdoctoral researcher in the University of Chicago from 2017 to 2019. He obtained his PhD degree in condensed matter physics from University of Minnesota in 2017, before which he graduated from Shanghai Jiao Tong University in 2010, with a bachelor’s degree in electrical engineering and minor’s degree in physics.