Evidence of topological nodal lines and surface states in the centrosymmetric superconductor SnTaS2

TL;DR

This paper demonstrates the existence of topological nodal-line states and surface states in the superconductor SnTaS2, revealing its potential for exploring topological fermions and superconductivity through combined experimental and theoretical methods.

Contribution

It provides the first evidence of topological nodal-line and surface states in the centrosymmetric superconductor SnTaS2 using ARPES and first-principles calculations.

Findings

Nodal lines formed by Ta 5d and Sn 5p bands near Fermi level

Surface states exhibit drumheadlike features

Spin-orbit coupling gaps out the nodal lines

Abstract

The discovery of signatures of topological superconductivity in superconducting bulk materials with topological surface states has attracted intensive research interests recently. Utilizing angle-resolved photoemission spectroscopy and first-principles calculations, here, we demonstrate the existence of topological nodal-line states and drumheadlike surface states in centrosymmetric superconductor SnTaS2, which is a type-II superconductor with a critical transition temperature of about 3 K. The valence bands from Ta 5d orbitals and the conduction bands from Sn 5p orbitals cross each other, forming two nodal lines in the vicinity of the Fermi energy without the inclusion of spin-orbit coupling (SOC), protected by the spatial-inversion symmetry and time-reversal symmetry. The nodal lines are gapped out by SOC. The drumheadlike surface states, the typical characteristics in nodal-line semimetals, are quite visible near the Fermi level. Our findings indicate that SnTaS2 offers a promising platform for exploring the exotic properties of the topological nodal-line fermions and gives a help to study topological superconductivity.