Moir{\'e} pattern assisted geometric resonant tunneling in disordered twisted bilayer graphene

TL;DR

This paper reveals a robust geometric resonance in twisted bilayer graphene caused by moiré supercells, which significantly influences quantum transport and can be tuned via the twist angle despite disorder.

Contribution

It demonstrates a new geometric resonance mechanism in disordered TBG systems linked to moiré supercells, independent of disorder strength and Fermi energy.

Findings

Resonant peaks in transmission occur at specific twist angles.

Resonance is due to bound states in moiré supercells.

Interlayer distance affects the resonance strength.

Abstract

We investigate the mesoscopic transport through a twisted bilayer graphene (TBG) consisting of a clean graphene nanoribbon on the bottom and a disordered graphene disc on the top. We show that, with strong top-layer disorder the transmission through such a device shows a sequence of resonant peaks with respect to the rotation angle $\theta$, where at the resonance angles $\theta_c$ the disc region contains one giant hexagonal moir{\'e} supercell. A further investigation shows that the value of $\theta_c$ shows negligible dependence on the disorder strength, the Fermi energy, and the shape distortion, indicating the resonance is a robust geometric feature of the moir{\'e} supercell. We explain this geometric resonance based on the bound states formed inside the moir{\'e} supercell, with their averaged local density of states dominating at the AA stacking region while minimizing at the AB stacking region. By increasing the interlayer distance, the peak becomes less pronounced which further confirms the role of interlayer coupling. The results presented here suggest a new mechanism to tune the quantum transport signal through the twist angle in disordered moir{\'e} systems.