Cavity-controlled superconductivity : interplay of matter and photonic fluctuations

Résumé :

Confining electromagnetic fields in a cavity reshapes the photonic environment of a superconductor, providing a tunable control of its superfluid stiffness. We show that the sign of this effect depends qualitatively on the underlying superconducting regime. In conventional low-temperature BCS superconductors, cavity-photon-mediated electron-electron interactions renormalize the kinetic mass of Cooper pairs, leading to a reduction of effective superfluid density near critical temperature. In contrast, in phase-fluctuating two-dimensional superconductors (such as underdoped cuprates), the cavity reshapes the collective plasma mode and can thereby suppress thermally excited phase fluctuations, effectively enhancing the superfluid stiffness. These theoretical findings provide a possible explanation for recent experimental observations in niobium- and cuprate-based systems.

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Contact : pierre.nataf@lpmmc.cnrs.fr