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TT: Fachverband Tiefe Temperaturen

TT 38: Topological Superconductors

TT 38.1: Hauptvortrag

Mittwoch, 18. März 2020, 11:00–11:30, HSZ 103

Nematic superconductivity in the superconducting doped topological insulators Nb_xBi₂Se₃ and Sr_xBi₂Se₃ — •Kristin Willa^{1, 2}, Matthew Smylie^{1, 3}, Roland Willa^{1, 2}, Ulrich Welp¹, Genda Gu⁴, and Wai-Kwong Kwok¹ — ¹Argonne National Laboratory, Lemont, USA — ²Karlsruhe Institute of Technology, Karlsruhe, Germany — ³Hofstra University, Hempstead, USA — ⁴Brookhaven National Laboratory, Upton, USA

Spontaneous rotational-symmetry breaking in the superconducting state of the doped topological insulator Bi₂Se₃ has attracted significant attention as a candidate for topological superconductivity. We have studied the normal and the superconducting state of Nb_xBi₂Se₃ and Sr_xBi₂Se₃ using magnetoresistance, magnetization, penetration depth and specific heat. While no sign of a symmetry breaking of the three-fold in plane crystal symmetry is observed in the normal state, we find a clear two-fold in plane symmetry of the upper critical field in the superconducting state. This large basal-plane anisotropy of H_c2 (Γ=3.5) is attributed to a two-component gap structure η = (η₁, η₂). A quantitative analysis of our data excludes more conventional sources of this twofold anisotropy and gives clear evidence for nematic superconductivity and some indications for topological superconductivity in both Nb_xBi₂Se₃ and Sr_xBi₂Se₃.