Band-unfolding approach to Moir\`e-induced band-gap opening and Fermi-level-velocity reduction in twisted bilayer graphene

TL;DR

This paper uses a band-unfolding method within a tight-binding model to analyze how Moiré patterns in twisted bilayer graphene induce energy gaps and reduce Fermi velocity, revealing the role of cone interactions.

Contribution

It introduces a band-unfolding approach to explain Moiré-induced electronic structure changes in twisted bilayer graphene, highlighting the mechanism behind band-gap opening and velocity reduction.

Findings

Identification of energy gaps at specific reciprocal space points.

Explanation of Fermi velocity reduction due to cone interactions.

Demonstration of Moiré pattern effects on electronic properties.

Abstract

We report on the energy spectrum of electrons in twisted bilayer graphene (tBLG) obtained by the band-unfolding method in the tight-binding model. We find the band-gap opening at particular points in the reciprocal space, that elucidates the drastic reduction of the Fermi-level velocity with the tiny twisted angles in tBLGs. We find that Moir\`e pattern caused by the twist of the two graphene layers generates interactions among Dirac cones, otherwise absent, and the resultant cone-cone interactions peculiar to each point in the reciprocal space causes the energy gap and thus reduced the Fermi-level velocity.