The direction of the d-vector in a nematic triplet superconductor

Abstract

We investigate the states of triplet pairing in a candidate nematic superconductor versus typical material parameters, using the mean field theory for two-and three-dimensional tight-binding models with local triplet pairing in the Eu representation of the D 3d, the point group of the system. In the two-dimensional model, the system favors the fully gapped chiral state for weaker warping or lower filling level, while a nodal and nematic δ4x state is favorable for stronger warping or higher filling, with the d-vector aligned along the principle axis. In the presence of lattice distortion, relative elongation along one of the principle axes,a, tends to rotate the nematic d-vector orthogonal to, resulting in the nematic δ4y state at sufficient elongation. Three-dimensionality is seen to suppress the chiral state in favor of the nematic ones. Our results may explain the variety in the probed direction of the d-vector in existing experiments.