Variations of Casimir energy from a superconducting transition

TL;DR

This paper investigates how the Casimir energy varies when a superconducting film transitions below its critical temperature, revealing potential impacts on superconductivity properties and contributing to debates on Casimir energy components.

Contribution

It introduces a five-layer Casimir cavity model with a superconducting film, showing how superconducting transition affects Casimir energy and critical magnetic field, addressing TE zero mode controversy.

Findings

Variation in Casimir energy correlates with superconducting transition.

Casimir energy variation can match the film's condensation energy.

The scheme offers insights into TE zero mode contributions.

Abstract

We consider a five-layer Casimir cavity, including a thin superconducting film. We show that when the cavity is cooled below the critical temperature for the onset of superconductivity, the sharp variation (in the microwave region) of the reflection coefficient of the film produces a variation in the value of the Casimir energy. Even though the relative variation in the Casimir energy is very small, its magnitude can be comparable to the condensation energy of the superconducting film, and thus causes a significant increase in the value of the critical magnetic field, required to destroy the superconductivity of the film. The proposed scheme might also help clarifying the current controversy about the magnitude of the contribution to Casimir free energy from the TE zero mode, as we find that alternative treatments of this mode strongly affect the shift of critical field.