Topological Surface States of 3D Topological Insulator on Twisted Bilayer Graphene

TL;DR

This paper theoretically investigates how moiré patterns from twisted bilayer graphene affect the topological surface states of Bi₂Se₃, revealing band structure modifications and potential for new topological phases.

Contribution

It provides a comprehensive theoretical analysis of the impact of moiré potentials on topological surface states in a heterostructure of Bi₂Se₃ and twisted bilayer graphene, including symmetry and perturbation analysis.

Findings

Moiré potential folds Dirac cone into moiré Brillouin zone.

Mini-gap openings and band flattening observed.

Potential emergence of secondary Dirac points.

Abstract

We present a comprehensive theoretical study of the topological surface states (TSS) of Bi$_2$Se$_3$, a 3D topological insulator, epitaxially grown on twisted bilayer graphene (tBG). The moir\'e potential induced by tBG folds the TSS Dirac cone into the moir\'e Brillouin zone (MBZ), resulting in mini-gap openings, band flattening, and the potential emergence of secondary Dirac points. Using effective field theory, symmetry analysis, and higher-order perturbation theory, we analyze both commensurate and incommensurate twist angles, revealing significant band structure reconstruction in periodic systems and quasi-periodic effects in incommensurate ones. This work provides deep insights into the interplay between topological protection and moir\'e modulation, offering a pathway to engineer novel topological phases.