Observation of spin-polarized surface states in the nodal-line semimetal SnTaS2

The superconductor SnTaS2 is theoretically predicted to be an intriguing topological nodal line semimetal without consideration of spin-orbit coupling. By carrying out angle-resolved photoemission (ARPES) and spin -resolved ARPES measurements combined with band structure calculations, we have provided a complete picture of the electronic structure and spin polarization property for the prominent surface states of SnTaS2. The low -energy electronic states are dominated by surface states; two of them are from the S-terminated surface, while four of them are from the Sn-terminated surface. These give rise to interesting Fermi surface topology of SnTaS2: three pockets located at Gamma over bar , M over bar and K over bar for the S-terminated surface and two pockets surrounding r and K over bar for the Sn-terminated surface. We further reveal that two surface states that cross the Fermi level are spin-polarized. Since SnTaS2 is also a superconductor, our observations indicate that it may provide a new platform to explore topological superconductivity and other exotic properties.