Nonuniform Spin Triplet Superconductivity due to Antisymmetric Spin-Orbit Coupling in Noncentrosymmetric Superconductor CePt$_3$Si

TL;DR

This paper demonstrates that antisymmetric spin-orbit coupling can stabilize a nonuniform spin triplet superconducting state in noncentrosymmetric materials like CePt$_3$Si, even without an external magnetic field, affecting physical properties.

Contribution

It reveals that antisymmetric spin-orbit coupling induces and stabilizes nonuniform FFLO states in spin triplet superconductors without magnetic fields, a novel mechanism in noncentrosymmetric systems.

Findings

Nonuniform superconducting state is stabilized by antisymmetric spin-orbit coupling.

Transition temperature is reduced by spin-orbit coupling, similar to magnetic pair breaking.

Physical quantities show power-law temperature dependence in the nonuniform state.

Abstract

We show that the nonuniform state (Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state) of the spin triplet superconductivity in noncentrosymmetric systems is stabilized by antisymmetric spin-orbit coupling even if the magnetic field is absent. The transition temperature of the spin triplet superconductivity is reduced by the antisymmetric spin-orbit coupling in general. This pair breaking effect is shown to be similar to the Pauli pair breaking effect due to magnetic field for the spin singlet superconductivity, in which FFLO state is stabilized near the Pauli limit (or Chandrasekhar-Clogston limit) of external magnetic field. Since there are gapless excitations in nonuniform superconducting state, some physical quantities such as specific heat and penetration depth should obey the power low temperature-dependences. We discuss the possibility of the realization of nonuniform state in CePt$_3$Si.