Nematic pinning of the superconducting state in the doped topological insulator SrxBi2Se3

Abstract

Abstract The discovery of a rotational symmetry breaking, or nematic, state in the superconducting doped topological insulator MxBi2Se3 (M = Cu, Sr, Nb) indicates a multicomponent superconducting order parameter which is topological. Many questions remain in this family of materials. In particular, the nematic axis of twofold symmetry is always pinned along one of three rotationally equivalent directions in the threefold symmetric basal plane in the rhombohedral crystal. Crystallographic strain has been proposed as the origin of the choice of pinning axis. Here, we discuss nematic pinning of the superconducting state, summarizing our magnetotransport, magnetization, penetration depth, and calorimetry measurements, which support the theoretical picture of topological superconductivity. We discuss the impact of controlled disorder via proton irradiation on the nematic superconducting state and discuss results of our multimodal technique for searching for crystallographic strain below 1 K via simultaneous diffraction and magnetotransport measurements.