Cavity-control of the Ginzburg-Landau stiffness in superconductors

TL;DR

This paper predicts that cavity confinement can control the superconducting order-parameter stiffness by renormalizing the Cooper-pair kinetic mass through photon-mediated interactions, especially in low-$T_c$ materials.

Contribution

It introduces a novel mechanism for tuning superconductor properties via cavity-enhanced light-matter coupling affecting the order-parameter stiffness.

Findings

Cavity confinement can significantly alter the superconducting coherence length and penetration depth.

Photon-mediated interactions lead to a renormalization of the Cooper-pair kinetic mass.

The effect is tunable by cavity length and is most pronounced in low-$T_c$ superconductors.

Abstract

Confining light around solids via cavities enhances the coupling between the electromagnetic fluctuations and the matter. We predict that in superconductors this cavity-enhanced coupling enables the control of the order-parameter stiffness, which governs key length scales such as the coherence length of Cooper pairs and the magnetic penetration depth. We explain this as a renormalization of the Cooper-pair kinetic mass caused by photon-mediated repulsive interactions between the electrons building the pair. This effect is generic for Bardeen-Cooper-Schriffer superconductors and is most pronounced in low-$T_c$ materials. The strength of this effect can be tuned via the length of the cavity and we estimate it to be sizable for cavities in the infrared range.