Correlation-induced symmetry-broken states in large-angle twisted bilayer graphene on MoS2

TL;DR

This study demonstrates that correlation-induced symmetry-broken states can be achieved in large-angle twisted bilayer graphene by engineering the dielectric environment and interlayer coupling, expanding the conditions for correlated phenomena beyond magic angles.

Contribution

The paper shows that strong correlation effects in twisted bilayer graphene can be realized at non-magic angles through substrate engineering and STM tip modulation, broadening the scope of correlated state studies.

Findings

Symmetry-broken states observed at 3.45° twist angle

Giant splitting of van Hove singularity peak

Stripe charge order indicating strong correlations

Abstract

Strongly correlated states are commonly emerged in twisted bilayer graphene (TBG) with magic-angle, where the electron-electron (e-e) interaction U becomes prominent relative to the small bandwidth W of the nearly flat band. However, the stringent requirement of this magic angle makes the sample preparation and the further application facing great challenges. Here, using scanning tunneling microscopy (STM) and spectroscopy (STS), we demonstrate that the correlation-induced symmetry-broken states can also be achieved in a 3.45{\deg} TBG, via engineering this non-magic-angle TBG into regimes of U/W > 1. We enhance the e-e interaction through controlling the microscopic dielectric environment by using a MoS2 substrate. Simultaneously, the bandwidth of the low-energy van Hove singularity (VHS) peak is reduced by enhancing the interlayer coupling via STM tip modulation. When partially filled, the VHS peak exhibits a giant splitting into two states flanked the Fermi level and shows a symmetry-broken LDOS distribution with a stripy charge order, which confirms the existence of strong correlation effect in our 3.45{\deg} TBG. Our result paves the way for the study and application of the correlation physics in TBGs with a wider range of twist angle.