Signatures of nematic superconductivity in doped Bi2Se3 under applied stress

Abstract

The MxBi2Se3 family are candidates for topological superconductors, where M could be Cu, Sr, or Nb. Twofold anisotropy has been observed in various experiments, prompting the interpretation that the superconducting state is nematic. However, it has since been recognized in the literature that a twofold anisotropy in the upper critical field Hc2 is incompatible with the naive nematic hypothesis. In this paper we study the Ginzburg-Landau theory of a nematic order parameter coupled with an applied stress, and classify possible phase diagrams. Assuming that the Hc2 puzzle is explained by a preexisting “pinning field,” we indicate how a stress can be applied to probe an extended region of the phase diagram, and verify if the superconducting order parameter is indeed nematic. We also explore the Josephson tunneling between the proposed nematic superconducting state and an s-wave superconductor. The externally applied stress is predicted to serve as an on/off switch to the tunneling current, and in a certain regime the temperature dependence of the critical current can be markedly different from that between two conventional s-wave superconductors.

Source-reported materials — not catalogue approval

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