Sliding-dependent electronic structures of alternating-twist tetralayer graphene

TL;DR

This study investigates how sliding geometries in alternating-twist tetralayer graphene influence its electronic properties, revealing dependencies of bandwidths, gaps, and topological features on sliding configurations, twist angle, and carrier density.

Contribution

It provides a detailed analysis of the sliding-dependent electronic structures and topological properties of alternating-twist tetralayer graphene near the magic angle, including optical responses and carrier density effects.

Findings

AA sliding favors narrow bands and gaps

AB sliding induces finite valley Chern numbers

Electronic structure is highly sensitive to carrier density in AA configuration

Abstract

We study the electronic structure of alternating-twist tetralayer graphene, especially near its magic angle $\theta = 1.75^\circ$, for different AA, AB, and SP sliding geometries at their middle interface that divides two twisted bilayer graphenes. This sliding dependence is shown for the bandwidths, band gaps, and $K$-valley Chern numbers of the lowest-energy valence and conduction bands as a function of twist angle and interlayer potential difference. Our analysis reveals that the AA sliding is most favorable for narrow bands and gaps, and the AB sliding is most prone to developing finite valley Chern numbers. We further analyze the linear longitudinal optical absorptions as a function of photon energy and the absorption map in the moir\'{e} Brillouin zone for specific transition energies. A self-consistent Hartree calculation reveals that the AA system's electronic structure is the most sensitive to variations in carrier density.