Nodeless superconductivity in a quasi-two-dimensional superconductor AuTe2Se4/3**Project supported by the Key Basic Research Program of China (Grant Nos. 2015CB921401 and 2016YFA0300503), the National Natural Science Foundation of China (Grant Nos. 11422429 and 11421404), China Postdoctoral Science Foundation (Grant No. 2016T90332), the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning, and STCSM of China (Grant

Abstract

We performed ultra-low temperature thermal conductivity measurements on the single crystal of a new gold-based quasi-two-dimensional superconductor AuTe2Se4/3, which has a superconducting transition temperature Tc = 2.70 K. A negligible residual linear term κ0/T in zero magnetic field is observed, which suggests fully gapped superconducting state. Furthermore, the field dependence of κ0/T is similar to that of the multi-band s-wave superconductor BaFe1.9Ni0.1As2 at low field. These results reveal multiple nodeless superconducting gaps in this interesting quasi-two-dimensional superconductor with Berezinsky–Kosterlitz–Thouless topological transition.