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 D3d, 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 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, , tends to rotate the nematic d-vector orthogonal to , resulting in the nematic 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.