Instability of the topological surface state in Bi$_2$Se$_3$ upon deposition of gold

TL;DR

This study investigates how gold deposition destabilizes the topological surface state in Bi$_2$Se$_3$, revealing atomic substitution and hybridization effects that open a gap at the Dirac point.

Contribution

It demonstrates that gold atoms substitute bismuth atoms and hybridize with surface states, causing instability and gap opening in the topological surface state.

Findings

Gold atoms substitute bismuth atoms in Bi$_2$Se$_3$.

Hybridization of gold d-states with surface states causes gap opening.

Surface state becomes unstable upon gold deposition.

Abstract

Momentum resolved photoemission spectroscopy indicates the instability of the Dirac surface state upon deposition of gold on the (0001) surface of the topological insulator Bi$_2$Se$_3$. Based on the structure model derived from extended x-ray absorption fine structure experiments showing that gold atoms substitute bismuth atoms, first principles calculations provide evidence that a gap appears due to hybridization of the surface state with gold d-states near the Fermi level. Our findings provide new insights into the mechanisms affecting the stability of the surface state.