Superconductivity at the highest transition temperature of 8.1 K in a simple cubic AuxSb1-x-yTey alloy system synthesized under high pressure

Abstract

We have investigated superconductivity and structure in a gold-antimony-tellurium ternary alloy system (AuxSb 1-x-yTey) synthesized under high pressure. We found that Au0.125Sb0.75Te0.125 and AuSb6Te when crystallized in simple cubic structures (α-Po type), which are reported to be semiconductors above 20 K, are superconductors with a transition temperature (Tc) of 6.7 K. The structure and Tc are mapped on an Au-Sb-Te triangular diagram. A β-Po-type rhombohedral structure appears before the crystal structure changes from As type (Sb) to α-Po type. Superconductivity is observed in the β-Po-type structure as well as in the α-Po-type structure. Tc increases with decreasing Te concentration toward the Te-free Au-Sb end of the diagram. A Tc of 8.1 K was achieved for the Au-Sb alloy with a typical composition of Au 0.15Sb0.85. This Tc value is the highest among materials with the α-Po-type structure under ambient pressure. Our Au 0.125Sb0.75Te0.125 sample exhibits a weak metallic behavior in resistivity. The discrepancy in the normal state resistivity behaviors between the previous study and ours must originate from a difference in the number of lattice defects in the samples. © 2014 IOP Publishing Ltd.