Probing the topological surface states in superconducting Sn₄Au single crystal: a magneto transport study

Materials exhibiting bulk superconductivity along with magnetoresistance (MR) in their normal state have emerged as suitable candidates for topological superconductivity. In this article, we report a flux free method to synthesize single crystal of topological superconductor candidate Sn₄Au. The phase purity and single crystalline nature are confirmed through various characterizations viz. x-ray diffraction, field emission scanning electron microscopy, selected area electron diffraction, and transmission electron microscopy. Chemical states of the constituent element viz. Sn and Au are analysed through x-ray photoelectron spectroscopy. Superconductivity in synthesized Sn₄Au single crystal is evident formρ-Tplot, for which the critical field (H_c) is determined throughρ-Hplot at 2 K i.e. just below critical temperatureT_c. A positive MR is observed inρ-Hmeasurements at different temperatures aboveT_c, viz. at 3 K, 5 K, 10 K and 20 K. Further, the magnetoconductivity (MC) is analysed by using Hikami-Larkin-Nagaoka formalism, which signifies the presence of weak antilocalization (WAL) effect in Sn₄Au. Angle dependent magneto-transport measurement has been performed to detect the origin of observed WAL effect in Sn₄Au single crystal. Normalized MC vsHcosθplot shows presence of topological surface states in the studied system. It is evident that Sn₄Au is a 2.6 K topological superconductor.