# Multiple topological Dirac cones in a mixed-valent Kondo semimetal: g-SmS

## TL;DR

This paper theoretically demonstrates that g-SmS exhibits multiple topological Dirac cones on different surface terminations, revealing diverse topological surface states and their characteristics in a mixed-valent Kondo semimetal.

## Contribution

It provides a comprehensive analysis of surface states in g-SmS, showing the coexistence of different topological phases and identifying multiple Dirac cones on various surfaces.

## Key findings

- (111) surface shows a clear gapless Dirac cone.
- (110) surface exhibits both TIs and TCI surface states.
- Multiple Dirac cones are characterized by mirror eigenvalues and Chern numbers.

## Abstract

We demonstrate theoretically that the golden phase of SmS ($g$-SmS), a correlated mixed-valent system, exhibits nontrivial surface states with diverse topology. It turns out that this material is an ideal playground to investigate different band topologies in different surface terminations. We have explored surface states on three different (001), (111), and (110) surface terminations. Topological signature in the (001) surface is not apparent due to a hidden Dirac cone inside the bulk-projected bands. In contrast, the (111) surface shows a clear gapless Dirac cone in the gap region, demonstrating the unambiguous topological Kondo nature of $g$-SmS. Most interestingly, the (110) surface exhibits both topological-insulator-type and topological-crystalline-insulator (TCI)-type surface states simultaneously. Two different types of double Dirac cones, Rashba-type and TCI-type, realized on the (001) and (110) surfaces, respectively, are analyzed with the mirror eigenvalues and mirror Chern numbers obtained from the model-independent \emph{ab initio} band calculations.