Paper detail

Ginzburg - Landau theory of the triplet superconductivity in 3D Dirac semi-metal

It was recently shown that conventional phonon-electron interactions induce triplet pairing states in time-reversal invariant 3D Dirac semi - metals provided magnetic impurities or exchange interactions are strong enough?. The order parameter in this case is a vector field. Starting from the microscopic model of the isotropic Dirac semi-metal, the Ginzburg-Landau energy for this field is derived using the Gor'kov technique. It was found that the transversal coherence length is much smaller than the longitudinal despite the isotropy. Several new features appear when an external field is applied. The Ginzburg - Landau model is used to investigate magnetic properties of such superconductors. Using the small deviation method the magnetic penetration depth was found also to be vastly different for longitudinal and transverse fluctuations. As a result the superconductor responds as type I to a transverse perturbation, while with respect to a longitudinal perturbation it behaves as type II. At large fields the order parameter orients itself perpendicular to the field direction. The triplet superconductor persists at arbitrarily high magnetic field (no upper critical magnetic field) like in some p wave superconductors.