Weak-field Hall Resistivity and Spin/Valley Flavor Symmetry Breaking in Magic-Angle Twisted Bilayer Graphene

TL;DR

This paper investigates how detailed band-structure effects influence flavor-symmetry-breaking and Fermi surface reconstructions in magic-angle twisted bilayer graphene, using magneto-transport measurements.

Contribution

It provides a detailed analysis of the impact of strain, tunneling, and band renormalizations on flavor symmetry breaking in twisted bilayer graphene.

Findings

Weak-field Hall resistivity reveals flavor symmetry breaking.

Fermi surface reconstructions are linked to band-structure details.

Magneto-transport measurements elucidate the role of interactions.

Abstract

Near a magic twist angle, the lowest energy conduction and valence bands of bilayer graphene moir\'e superlattices become extremely narrow. The band dispersion that remains is sensitive to the moir\'e's strain pattern, nonlocal tunneling between layers, and filling-factor dependent Hartree and exchange band renormalizations. In this article we analyze the influence of these band-structure details on the pattern of flavor-symmetry-breaking observed in this narrow band system, and on the associated pattern of Fermi surface reconstructions revealed by weak-field-Hall and Schubnikov-de Haas magneto-transport measurements.