Dynamical instability towards finite-momentum pairing in quenched BCS superconducting phases

TL;DR

This paper investigates how quenched phase imprinting affects BCS superconductivity, revealing conditions under which finite-momentum pairing instability occurs or is suppressed, with implications for realizing exotic superconducting phases.

Contribution

It introduces a numerical analysis of phase imprint effects on BCS pairing, highlighting the conditions leading to finite-momentum pairing instability and differences between gauge potential types.

Findings

Weak phase imprint preserves BCS pairing.

Strong phase imprint can induce finite-momentum pairing instability.

Pulsed gauge potential prevents instability even at high vector potentials.

Abstract

In this work we numerically investigate the fate of the Bardeen-Cooper-Schrieffer (BCS) pairing in the presence of quenched phase under Peierls substitution using time-dependent real space and momentum space Bogoliubov-de Gennes equation methods and Anderson pseudospin representation method. This kind of phase imprint can be realized by modulating electric field in ultracold atoms and illumining of THz optical pump pulse in solids with conventional and unconventional superconductors. In the case of weak phase imprint, the BCS pairing is stable; while in the strong phase imprint, instability towards finite-momentum pairing is allowed, in which the real space and momentum space methods yield different results. In the pulsed gauge potential, we find that this instability will not happen even with much stronger vector potential. We also show that the uniform and staggered gauge potentials yield different behaviors. While the staggered potential induces transition from the BCS pairing to over-damped phase, the uniform gauge may enhance the pairing and will not induce to the over-damped phase. These result may shade light on the realization of finite momentum pairing, such as Fulde-Ferrell-Larkin-Ovchinnikov phase with dynamical modulation.