Topological phase transition and quantum spin Hall edge states of antimony few layers

TL;DR

This paper reports the discovery and analysis of a new two-dimensional topological insulator material, antimony few-layer films, demonstrating topological phase transition and quantum spin Hall edge states through experimental and theoretical methods.

Contribution

It introduces antimony few-layer films as a new 2D topological insulator and confirms topological phase transition and edge states via experiments and density-functional-theory calculations.

Findings

Robust edge states observed in Sb few-layer films

Topological phase transition predicted between three and four bilayers

Theoretical confirmation of non-trivial topological phase transition

Abstract

While two-dimensional topological insulators (2D TI) initiated the field of topological materials, only very few materials were discovered to date and the direct access to their quantum spin Hall edge states has been challenging due to material issues. Here, we introduce a new 2D TI material, Sb few layer films. Electronic structures of ultrathin Sb islands grown on Bi2Te2Se are investigated by scanning tunneling microscopy. The maps of local density of states clearly identify robust edge electronic states over the thickness of three bilayers in clear contrast to thinner islands. This indicates the topological edge states emerged through a 2D topological phase transition predicted between three and four bilayer films in recent theory. The non-trivial phase transition and edge states are confirmed for epitaxial films by extensive density-functional-theory calculations. This work provides an important material platform to exploit miscroscopic aspects of the quantum spin Hall phase and its quantum phase transition.