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

TL;DR

This paper demonstrates that magnetic impurities can stabilize triplet superconductivity in 3D Dirac semimetals, especially near the Dirac point, where the competition between singlet and triplet pairing is sensitive to interactions.

Contribution

It reveals that magnetic impurities favor odd (triplet) pairing in Dirac semimetals close to the Dirac point, providing insight into impurity effects on unconventional superconductivity.

Findings

Magnetic impurities stabilize triplet pairing near the Dirac point.

Singlet pairing energy is marginally lower than triplet in certain parameter ranges.

Impurity effects can determine the superconducting order in Dirac semimetals.

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 $\mu $ and parameters characterizing the pairing attraction (effective electron-electron coupling constant $\lambda $ and the Debye energy $T_{D}$) 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 ($\mu \lesssim T_{D}$) magnetic impurities stabilize the odd pairing superconducting state.