Topological States on the Gold Surface

TL;DR

This paper reinterprets gold surface states as topologically derived surface states, revealing topological properties in noble metals and suggesting implications for surface chemistry and catalysis.

Contribution

It demonstrates that Shockley surface states on gold are actually topologically derived, providing a new topological perspective on noble metal surface states.

Findings

Gold surface states are topologically derived surface states.

Topological invariants characterize noble metal surface states.

Topological states are present on surfaces of other noble metals.

Abstract

Gold surfaces host special electronic states that have been understood as a prototype of Shockley surface states (SSs). These SSs are commonly employed to benchmark the capability of angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling spectroscopy. We find that these Shockley SSs can be reinterpreted as topologically derived surface states (TDSSs) of a topological insulator (TI), a recently discovered quantum state. Based on band structure calculations, the Z2 topological invariant can be well defined to characterize the nontrivial features of gold that we detect by ARPES. The same TDSSs are also recognized on surfaces of other well-known noble metals (e.g., silver, copper, platinum, and palladium). Besides providing a new understanding of noble metal SSs, finding topological states on late transition metals provokes interesting questions on the role of topological effects in surface-related processes, such as adsorption and catalysis.