Periodicity-free unfolding method of electronic energy spectra: Application to twisted bilayer graphene

TL;DR

This paper introduces a new unfolding method for electronic energy spectra that eliminates dependence on the simulation cell, enabling more accurate comparisons with experimental ARPES data, demonstrated on various models including twisted bilayer graphene.

Contribution

The paper presents a novel periodicity-free unfolding technique for electronic spectra, independent of the simulation cell choice, applicable to complex materials like twisted bilayer graphene.

Findings

The method produces spectra consistent across different simulation cells.

Validated on models including twisted bilayer graphene.

Shows direct relevance to ARPES experimental spectra.

Abstract

We propose a novel periodicity-free unfolding method of the electronic energy spectra. Our new method solves a serious problem that calculated electronic band structure strongly depends on the choice of the simulation cell, i.e., primitive-cell or supercell. The present method projects the electronic states onto the free-electron states, giving rise to the {\it plane-wave unfolded} spectra. Using the method, the energy spectra can be calculated as a completely independent quantity from the choice of the simulation cell. We have examined the unfolded energy spectra in detail for three models and clarified the validity of our method: One-dimensional interacting two chain model, monolayer graphene, and twisted bilayer graphene. Furthermore, we have discussed that our present method is directly related to the experimental ARPES (Angle-Resolved Photo-Emission Spectroscopy) spectra.