Pseudospin triplet superconductivity in 2H-type transition-metal dichalcogenide monolayers

We study the pseudospin of an electron pair in superconducting transition-metal dichalcogenide monolayers. We show that the pseudospin affects the electric transport property of the lateral heterojunction of the superconducting and metallic monolayers by using both analytic and numerical methods. The pseudospins of two electrons forming a Cooper pair are parallel to each other, unlike the real spin, which is antiparallel, and the direction of parallel pseudospins varies with the Fermi energy. The pseudospin is aligned in the same direction for the Fermi energy close to the valence band top, but it has a chiral configuration in the wave number space for the Fermi energy far from the band edge. Moreover, we investigate the electronic transport with the formation of a Cooper pair, the Andreev reflection, in a lateral heterojunction of semiconducting and superconducting transition-metal dichalcogenides, MoSe2 and NbSe2 monolayers with charge doping, respectively. The conductance decreases with the superconducting transition under the electron-doped and slightly hole doped junctions for the slight source-drain bias. However, in the highly hole doped junction, the junction shows an increase of conductance with the transition. We reveal that the qualitative change in the electronic transport property is attributed to the variation of the pseudospin configuration in the Fermi surface with the charge density.