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

Abstract

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 (XRD), field emission scanning electron microscopy (FESEM), selected Area electron diffraction (SAED), and transmission electron microscopy (TEM). Chemical states of the constituent element viz. Sn and Au are analyzed through X-Ray photoelectron spectroscopy (XPS). Superconductivity in synthesized Sn4Au single crystal is evident form -T plot and critical field (Hc) is determined through -H plot at 2K i.e., just below critical temperature Tc. A positive magnetoresistance (MR) is observed in -H measurements at different temperatures above Tc, viz. at 3K, 5K, 10K and 20K. Further, the magnetoconductivity (MC) is analyzed by using Hikami-Larkin-Nagaoka (HLN) 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 vs Hcosplot shows presence of topological surface states (TSS) in the studied system. It is evident that Sn4Au is a 2.6K topological superconductor.

Two-fold anisotropic superconducting state in topological superconductor Sn4Au

“…According to the fitting parameters obtained from the Rietveld refinement, XRD peaks are more fitted in the Aea2 space group. The previous experimental reports on Sn 4 Au [18,25,28] also suggest the same to be crystallized in Aea2 space group symmetry.…”

“…-Single crystalline Sn 4 Au has been synthesized using a simple melt growth method. The details of heat treatment followed in the synthesis of Sn 4 Au single crystals were reported earlier by us [25]. Rigaku mini flex II tabletop XRD equipped with Cu K α radiation has been used to record the XRD pattern on mechanically cleaved crystal flake and powdered sample.…”

Non-trivial band topology in the superconductor AuSn4: a first principle study

“…The crystal structure of AuSn 4 is orthorhombic, but in literature the space groups are found to be Aea2 and Ccce space group. The most of the old as well as recent experimental results show AuSn 4 to have Aea2 space group symmetry [33,41,47,48]. However in online database the space group is found to be Ccce [49,50].…”

“…The symmetrized unit cell parameters taken from the materials project database [49] for Ccce space group are a = 6.682 (3) Å, b = 11.871 (5) Å, c = 6.658 (2) Å and α = β = γ = 90 0 . For Aea2 type space group, experimentally obtained unit cell parameters were obtained from a very recent experimental report on the studied system [48]. The cell parameters and atomic positions for both cases are shown in tables 1 and 2 respectively.…”

Band structure, superconductivity, and polytypism in AuSn4

“…PtSn 4 and PdSn 4 are not superconducting, * Corresponding author: edwin.herrera@uam.es but AuSn 4 is superconducting with a critical temperature of T c = 2.35 K [15]. The question if superconductivity in AuSn 4 is unconventional is important in the light of the anomalous band structure properties of PtSn 4 and PdSn 4 [16][17][18]. A recent examination of the bulk and transport properties of single crystals of AuSn 4 provides a clear specific heat jump at the superconducting transition.…”