Landau Levels of Bilayer Graphene in a WSe$_2$/Bilayer Graphene van der Waals Heterostructure

TL;DR

This study reveals how a WSe$_2$ layer influences the Landau level energies and quantum Hall effects in bilayer graphene, showing potential for engineering electronic properties through van der Waals heterostructures.

Contribution

It provides a systematic analysis of Landau level modifications in bilayer graphene when interfaced with WSe$_2$, highlighting the impact on energy gaps and phase diagrams.

Findings

Enhanced exchange-driven energy splitting at certain filling factors.

Modified phase diagram at filling factor ν=0.

Reduced spin gap at ν=2 by approximately two-fold.

Abstract

Heterostructures formed between two different van der Waals materials enable interactions and functionalities absent in each component. In this work we show that vicinity to an atomically thin WSe$_2$ sheet dramatically impacts the energies of the symmetry-broken low Landau levels of bilayer graphene, possibly due to screening. We present a systematic study of the magnetic field and electrical displacement field dependences of the Landau level gaps at filling factor $\nu$ = 1, 2, 3, and compare to BN encapsulated pristine bilayer graphene. The exchange-dominated energy splitting between the N = 0 and 1 orbital wave functions is significantly enhanced, which leads to a modified phase diagram at filling factor $\nu$ = 0 and larger energy gaps at $\nu$ = 1 and 3 in WSe$_2$/bilayer graphene heterostructures. The exchange-enhanced spin gap at $\nu$ = 2, on the other hand, is reduced by approximately two-fold. Our results demonstrate a possible way to engineer quantum Hall phenomena via van der Waals heterostructures.