Electrodynamics of Superconductors Exposed to High Frequency Fields

TL;DR

This paper analyzes the mechanisms of electric losses in superconductors subjected to high-frequency magnetic fields, focusing on normal-conducting components, depairing effects, and vortex motion.

Contribution

It provides a detailed examination of loss origins in superconductors under RF fields, highlighting the roles of normal currents, depairing, and vortex dynamics.

Findings

Normal-conducting components cause frequency-squared losses.

Superconductivity breaks down near the depairing current.

Vortex penetration leads to significant AC losses.

Abstract

The electric losses in a bulk or film superconductor exposed to a parallel radio-frequency magnetic field may have three origins: In homogeneous vortex-free superconductors losses proportional to the frequency squared originate from the oscillating normal-conducting component of the charge carriers which is always present at temperatures $T>0$. With increasing field amplitude the induced supercurrents approach the depairing current at which superconductivity breaks down. And finally, if magnetic vortices can penetrate the superconductor they typically cause large losses since they move driven by the AC supercurrent.