Direct observation of decoupled Dirac states at the interface between topological and normal insulators

TL;DR

This study uses angle-resolved photoelectron spectroscopy to directly observe and characterize Dirac states at the interface between topological and normal insulators, confirming their presence and energy separation.

Contribution

It provides direct experimental evidence of Dirac fermions at the topological-normal-insulator interface and analyzes band bending effects in heterostructures.

Findings

Dirac fermions are present at the topological-normal-insulator interface.

Dirac states are absent at the topological-topological-insulator interface.

Band bending causes energy separation of interface and surface states.

Abstract

Several proposed applications and exotic effects in topological insulators rely on the presence of helical Dirac states at the interface between a topological and a normal insulator. In the present work, we have used low-energy angle-resolved photoelectron spectroscopy to uncover and characterize the interface states of Bi$_2$Se$_3$ thin films and Bi$_2$Te$_3$/Bi$_2$Se$_3$ heterostuctures grown on Si(111). The results establish that Dirac fermions are indeed present at the topological-normal-insulator boundary and absent at the topological-topological-insulator interface. Moreover, it is demonstrated that band bending present within the topological-insulator films leads to a substantial separation of the interface and surface states in energy. These results pave the way for further studies and the realization of interface-related phenomena in topological-insulator thin-film heterostructures.