Manipulation of Topological States and Bulk Band Gap Using Natural Heterostructures of a Topological Insulator

TL;DR

This study uses angle-resolved photoemission spectroscopy to investigate natural heterostructures of topological insulators, revealing tunable topological states, enhanced bulk band gaps, and a topological phase transition, advancing quantum material applications.

Contribution

It demonstrates that natural heterostructures can manipulate topological states and bulk band gaps, introducing a new approach for designing topological insulator-based devices.

Findings

Gapped Dirac-cone state observed at m=2

Bulk band gap enhanced to 0.5 eV

Topological phase transition between m=1 and m=2

Abstract

We have performed angle-resolved photoemission spectroscopy on (PbSe)5(Bi2Se3)3m, which forms a natural multilayer heterostructure consisting of a topological insulator (TI) and an ordinary insulator. For m = 2, we observed a gapped Dirac-cone state within the bulk-band gap, suggesting that the topological interface states are effectively encapsulated by block layers; furthermore, it was found that the quantum confinement effect of the band dispersions of Bi2Se3 layers enhances the effective bulk-band gap to 0.5 eV, the largest ever observed in TIs. In addition, we found that the system is no longer in the topological phase at m = 1, pointing to a topological phase transition between m = 1 and 2. These results demonstrate that utilization of naturally-occurring heterostructures is a new promising strategy for realizing exotic quantum phenomena and device applications of TIs.