Speaker: Tomohiro Soejima (UC Berkeley)

Date & Time: 10am, Feb 10, 2021.

Title: Identifying strongly-interacting phases of twisted bilayer graphene with cutting-edge numerics

Abstract: Magic-angle twisted bilayer graphene (MATBG) has been shown to host a variety of interesting phases at different doping levels, the most prominent of which is superconductivity. Many of these phases are believed to be driven by strong electron-electron interaction, and there has been ongoing efforts to understand it both numerically and analytically.

In this talk, we will focus on density matrix renormalization group (DMRG) method, which is suitable for describing strongly-correlated ground states. It is prohibitively expensive to perform DMRG for MATBG with conventional approaches, and we introduce a new "MPO compression" scheme that overcomes that challenge. Using this setup, we show that the ground state of MATBG at certain integer fillings undergo a phase transition between a phase with intervalley coherence (a so-called Kramers inter-valley coherent state) to a nematic semimetal. These results show the ability of our DMRG scheme to access ground state information of DMRG that has otherwise been inaccessible.