Strain-induced large injection current in twisted bilayer graphene

TL;DR

This paper predicts that strained twisted bilayer graphene with broken sublattice symmetry can generate large, tunable injection currents under circularly polarized light, especially in the THz regime, due to Berry curvature effects.

Contribution

It introduces the prediction of large, controllable injection currents in strained TBG with broken symmetry, driven by Berry curvature dipoles, and explores their potential for THz applications.

Findings

Large injection currents can be induced in strained TBG.

Injection currents are tunable by chemical potential and light helicity.

TBG shows strong responses in the THz frequency range.

Abstract

The electronic wavefunctions in moir\'e materials are highly sensitive to the details of the local atomic configuration enabling Bloch band geometry and topology to be controlled by stacking and strain. Here we predict that large injection currents (under circular polarized irradiation) can develop in strained twisted bilayer graphene (TBG) heterostructures with broken sublattice symmetry; such bulk photovoltaic currents flow even in the absence of a p-n junction and can be controlled by the helicity of incident light. As we argue, large injection current rates proceed from strong and highly peaked interband Berry curvature dipole distributions (arising from the texturing of Bloch wavefunctions in strained TBG heterostructures). Strikingly, we find that TBG injection current displays pronounced responses in the THz regime and can be tuned by chemical potential. These render injection currents a useful photocurrent probe of symmetry breaking in TBG heterostructures and make TBG a promising material for THz technology.