Direction and symmetry transition of the vector order parameter in topological superconductors Cu x Bi2Se3

Abstract

The understanding of the vector order parameter for Cu0.3Bi2Se3 topological superconductor remains unclear. Here, Kawai et al. report a surprising disappearance of the in-plane upper critical field anisotropy for Cu x Bi2Se3 single crystals with more carriers, indicating a transition from nematic to chiral superconducting gap symmetry.