Electronic Band Structure and Superconducting Properties of SnAs

TL;DR

This study combines experimental and theoretical methods to analyze the electronic structure and superconducting behavior of SnAs, confirming its conventional BCS superconductivity with an isotropic s-wave gap.

Contribution

It provides a comprehensive analysis of SnAs's electronic band structure and superconducting properties, including ARPES, DFT calculations, and various measurements, highlighting its conventional superconductivity.

Findings

ARPES and DFT show better agreement with (111) slab models.

Superconducting gap is consistent with single-band BCS theory.

No evidence of unconventional superconductivity despite spin-orbit coupling.

Abstract

We report comprehensive study of physical properties of the binary superconductor compound SnAs. The electronic band structure of SnAs was investigated using both angle-resolved photoemission spectroscopy (ARPES) in a wide binding energy range and density functional theory (DFT) within generalized gradient approximation (GGA). The DFT/GGA calculations were done including spin-orbit coupling for both bulk and (111) slab crystal structures. Comparison of the DFT/GGA band dispersions with ARPES data shows that (111) slab much better describes ARPES data than just bulk bands. Superconducting properties of SnAs were studied experimentally by specific heat, magnetic susceptibility, magnetotransport measurements and Andreev reflection spectroscopy. Temperature dependences of the superconducting gap and of the specific heat were found to be well consistent with those expected for the single band BCS superconductors with an isotropic s-wave order parameter. Despite spin-orbit coupling is present in SnAs, our data shows no signatures of a potential unconventional superconductivity, and the characteristic BCS ratio $2\Delta/T_c = 3.48 - 3.73$ is very close to the BCS value in the weak coupling limit.