Pair-density wave states through spin-orbit coupling in multilayer superconductors

TL;DR

This paper investigates how spin-orbit coupling and magnetic fields induce a transition from uniform to pair-density wave states in multilayer superconductors, revealing novel phase behavior and potential experimental realizations.

Contribution

It demonstrates the emergence of layer-dependent pair-density wave states driven by spin-orbit coupling and magnetic fields in multilayer superconductors, a novel phase transition mechanism.

Findings

First-order phase transition between BCS and pair-density wave states.

Layer-dependent order parameters with sign change at high fields.

Additional features in the phase diagram due to paramagnetic effects.

Abstract

Spin singlet superconductors with quasi-two dimensional multilayer structure are studied in high magnetic fields. Specifically we concentrate on bi- and tri-layer systems whose layers by symmetry are subject Rashba-type spin-orbit coupling. The combination of magnetic field and spin-orbit coupling leads to a first order phase transition between different states of layer-dependent superconducting order parameters upon rising the magnetic field. In this context we distinguish the low-field Bardeen-Cooper-Schrieffer state where all layers have order parameters of the same sign and the high-field pair-density wave state where the layer-dependent order parameters change the sign at the center layer. We also show that progressive paramagnetic limiting effects yield additional features in the H-T phase diagram. As possible realizations of such unusual superconducting phases we consider artificial superlattices of CeCoIn_5, as well as some multilayer high-T_c cuprates.