Response of the topological surface state to surface disorder in TlBiSe$_2$

TL;DR

This study investigates how surface disorder in TlBiSe$_2$ affects its topological surface states, revealing their robustness and providing insights into surface phenomena and doping effects.

Contribution

It provides experimental evidence of the topological surface state's resilience to surface disorder in TlBiSe$_2$ and clarifies the nature of surface termination.

Findings

Topmost layer forms Tl islands at low temperature and mobile Tl atoms at room temperature.

No trivial surface states observed at low temperatures, indicating surface disorder does not destroy topological states.

Topological surface state remains clearly observable despite surface irregularities.

Abstract

Through a combination of experimental techniques we show that the topmost layer of the topo- logical insulator TlBiSe$_2$ as prepared by cleavage is formed by irregularly shaped Tl islands at cryogenic temperatures and by mobile Tl atoms at room temperature. No trivial surface states are observed in photoemission at low temperatures, which suggests that these islands can not be re- garded as a clear surface termination. The topological surface state is, however, clearly resolved in photoemission experiments. This is interpreted as a direct evidence of its topological self-protection and shows the robust nature of the Dirac cone like surface state. Our results can also help explain the apparent mass acquisition in S-doped TlBiSe$_2$.