Twist Angle-Dependent Bands and Valley Inversion in 2D Materials/hBN Heterostructures

TL;DR

This study demonstrates that the electronic band structure and valley properties of 2D materials in hBN heterostructures can be systematically tuned by adjusting the twist angle and substrate configuration, revealing new avenues for device engineering.

Contribution

It reveals that twist angle and substrate modifications can controllably alter band structures and valley inversion in 2D heterostructures, challenging previous assumptions.

Findings

Band structures are tunable by twist angle even at large angles.

Substrate addition/removal causes valley inversion in TLG.

Substrate and twist angle engineering enable band and valley control.

Abstract

The use of relative twist angle between adjacent atomic layers in a van der Waals heterostructure, has emerged as a new degree of freedom to tune electronic and optoelectronic properties of devices based on 2D materials. Using ABA-stacked trilayer (TLG) graphene as the model system, we show that, contrary to conventional wisdom, the band structures of 2D materials are systematically tunable depending on their relative alignment angle between hexagonal BN (hBN), even at very large twist angles. Moreover, addition or removal of the hBN substrate results in an inversion of the K and K' valley in TLG's lowest Landau level (LL). Our work illustrates the critical role played by substrates in van der Waals heterostructures and opens the door towards band structure modification and valley control via substrate and twist angle engineering.