Electric field tunable bands in doubly aligned bilayer graphene hBN moire superlattice

TL;DR

This paper demonstrates how an external electric field can modify the electronic bands in an asymmetrically twisted hBN/BLG/hBN supermoire, revealing field-controlled band gaps and Landau levels, with implications for tunable electronic properties.

Contribution

It introduces the first detailed study of electric field effects on an asymmetrically twisted hBN/BLG/hBN supermoire, highlighting asymmetric band modifications and new quantum Hall features.

Findings

Field-controlled layer polarization observed.

D-dependent additional band gaps identified.

New 6-fold degenerate Landau levels detected.

Abstract

In this letter, we demonstrate electric field-induced band modification of an asymmetrically twisted hBN/BLG/hBN supermoire lattice. Distinct from unaligned BLG/hBN systems, we observe regions in the density-displacement field (n-D) plane where the device conductance is independent of n and decreases as |D| increases. This distinction arises due to the angle asymmetry between the layers, which induces field-controlled layer polarization. We identify D-dependent additional band gaps near the charge neutrality point that appear in the conduction (valence) band for negative (positive) D values. In the quantum Hall regime, new 6-fold degenerate Landau levels are observed. Our findings establish that in an asymmetric supermoire heterostructure, an external vertical displacement field affects the valence and conduction bands very differently and sheds light on the asymmetric conductance patterns noted in previous studies.