Interacting models for twisted bilayer graphene: a quantum chemistry approach

Lin Lin
University of California, Berkeley (UC Berkeley)

The nature of the correlated states in twisted bilayer graphene (TBG) at the magic angle has received intense attention in recent years. We present a numerical study of an interacting Bistritzer-MacDonald (IBM) model of TBG using a suite of methods in quantum chemistry, including Hartree-Fock, coupled cluster singles, doubles (CCSD) and perturbative triples (CCSD(T)), as well as a quantum chemistry version of the density matrix renormalization group method (QC-DMRG). Our treatment of TBG is agnostic to gauge choices, and we present a new gauge-invariant formulation to detect the spontaneous symmetry breaking in interacting models. As part of our benchmarking, we explore the impact of different schemes for removing ``double-counting'' in the IBM model. Our results suggest that cross-validation of different IBM models, and perhaps ab initio interacting models may be needed for future studies of the TBG system.

Presentation (PDF File)

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