Superconductivity in magnetic multipole states

TL;DR

This paper explores how magnetic multipole orders in noncentrosymmetric metals can stabilize various unconventional superconducting states, including topological and FFLO states, driven by spin-orbit coupling and magnetic symmetry breaking.

Contribution

It demonstrates the stabilization of different superconducting states in magnetic multipole ordered systems and identifies the topological nature of the PDW state.

Findings

PDW state is a topological superconductor with nontrivial $bZ_2$ and winding numbers.

FFLO state arises without macroscopic magnetic moment due to asymmetric band structure.

Magnetic multipole orders induce diverse superconducting phases in noncentrosymmetric metals.

Abstract

Stimulated by recent studies of superconductivity and magnetism with local and global broken inversion symmetry, we investigate the superconductivity in magnetic multipole states in locally noncentrosymmetric metals. We consider a one-dimensional zigzag chain with sublattice-dependent antisymmetric spin-orbit coupling and suppose three magnetic multipole orders: monopole order, dipole order, and quadrupole order. It is demonstrated that the Bardeen-Cooper-Schrieffer state, the pair-density wave (PDW) state, and the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state are stabilized by these multipole orders, respectively. We show that the PDW state is a topological superconducting state specified by the nontrivial $\mathbb{Z}_2$ number and winding number. The origin of the FFLO state without macroscopic magnetic moment is attributed to the asymmetric band structure induced by the magnetic quadrupole order and spin-orbit coupling.