Electronic band structure and superconducting properties of SnAs

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∆/Tc = 3.48 − 3.73 is very close to the BCS value in the weak coupling limit.

Andreev reflection spectroscopy on SnAs single crystals

“…By fitting the Andreev reflection spectra we estimate ∆ to be ∼ 0.62 meV. This is in accordance with the results obtained by Bezotosnyi et al [5].…”

“…This wide open M-H loop shows the observed superconductivity in synthesized sample is type-II superconductivity. All previous reports shows SnAs to be a type-I superconductor with a critical field of 150Oe [5,11]. In this result M-H loop starts to deviate from linearity from around 60 Oe and it closes at around 290 Oe.…”

“…Moreover, DFT calculations revealed that spin-orbit coupling does not have any significant effect on the bandstructure. However, ARPES measurements revealed significant band splitting [5] . More recent investigation of electronic band structure and Density of States(DOS) within the Density Functional Theory (DFT) posited the possibility of non-trivial topology in SnAs bands.…”

“…These materials exhibit novel properties and are considered as sister compounds of topological materials (e.g. topological semimetals and topologcial crystalline insulators), while some were also found to be superconductors [5]. The SnT family of compounds are also candidate materials for topological superconductivity.…”

Novel magnetic stoichiometric superconductor EuRbFe4As4

“…Andreev reflection spectroscopy was measured using the break-junction technoque (BJ) [28][29][30][31][32][33]. For measurements, the sample shaped as a flat plate (in the ab plane) was attached to an isolated springy sample stage made of Be-bronze.…”