Wannier center spectroscopy to identify boundary-obstructed topological insulators

TL;DR

This paper introduces an experimental method to locate Wannier centers in artificial lattices, aiding the identification of boundary-obstructed topological insulators by linking Wannier center positions to topological properties.

Contribution

It presents a novel experimental approach to determine Wannier centers in artificial lattices, providing a new way to identify topological phases beyond traditional invariants.

Findings

Successfully determined Wannier centers in various 1D chains

Corroborated experimental results with tight-binding simulations

Identified boundary-obstructed topological insulators using Wannier centers

Abstract

The hallmark of topological crystalline insulators is the emergence of a robust electronic state in a bandgap localized at the boundary of the material. However, end, edge, and surface states can also have a nontopological origin. Unfortunately, topological invariants such as the winding number and Zak phase are often not directly experimentally accessible for solids. In addition to topological invariants, the position of the Wannier centers provides a fingerprint for the topological character of a material. Here, we demonstrate a method to experimentally determine the location of Wannier centers in artificial lattices made of Cs/InAs(111)A by integrating the density of states. We determine the locations of the Wannier centers for various 1D chains, topological and trivial, and corroborate our findings with tight-binding simulations.