Magnetic impurities make superconductivity in 3D Dirac semi-metal triplet

Abstract

Conventional electron-phonon coupling induces either odd (triplet) or even (singlet) pairing states in a time reversal and inversion invariant Dirac semi -metal. In certain range of the chemical potential µ and parameters characterizing the pairing attraction (effective electronelectron coupling constant λ and the Debye energy TD) the energy of the singlet although always lower, prevails by a very slim margin over the triplet. This means that interactions that are small but discriminate between the spin singlet and the spin triplet determine the nature of the superconducting order there. It shown that in materials close enough to the Dirac point ( µ TD) magnetic impurities stabilize the odd pairing superconducting state.

Strong magnetic field induces superconductivity in a Weyl semimetal

“…However, although they are nearly degenerate in some cases (very small chemical potential µ), the singlet always prevail energetically. It was also shown theoretically 27 that magnetic impurities or proximity to the Stoner instability (local magnetic moment due to the exchange interaction) can favor the triplet state. In such case the triplet superconducting state in WSM must survive in extremely strong magnetic fields.…”