Non-equilibrium $d-$ wave pair density wave order parameter in superconducting cuprates

TL;DR

This paper explores the behavior of non-equilibrium pair density wave order in cuprate superconductors, revealing oscillations and coexistence phenomena that extend understanding of their dynamic properties.

Contribution

It introduces a microscopic model demonstrating non-equilibrium oscillations and metastable coexistence of $d$-wave superconductivity and pair density waves.

Findings

Oscillations at about $2\Delta/\hbar$ frequency in weak nonequilibrium.

Metastable coexistence of $d$-wave superconductivity and pair density wave gaps.

Transition to nonlinear regime with complex order parameter dynamics.

Abstract

We investigate the nonequilibrium pair density wave order parameter in a simple microscopic model with the ground state $d-$ wave spatially uniform superconductivity. After pushing the system out of equilibrium by a short-time induced order parameter, the system can exhibit robust free nondecaying oscillations of nonuniform superconducting order. In the weak nonequilibrium regime, the frequency of these oscillations is about $2\Delta/\hbar$ and the amplitude can be explained qualitatively by features of equilibrium free energy. In case when the system was taken far from equilibrium, it transits to a non-linear regime where even metastable coexistence of $d-$ wave superconducting and pair density wave gaps are possible.