Critical-state effects on microwave losses in type-II superconductors

TL;DR

This paper investigates how the critical state in type-II superconductors affects microwave energy losses, emphasizing the importance of considering vortex magnetic field distribution to accurately interpret experimental data.

Contribution

It introduces a detailed analysis of the critical state effects on microwave losses using the Coffey and Clem model, highlighting their significance in experimental interpretation.

Findings

Critical state effects significantly influence microwave surface resistance.

The model accurately explains experimental data in bulk niobium.

Vortex magnetic field distribution is crucial for understanding energy losses.

Abstract

We discuss the microwave energy losses in superconductors in the critical state. The field-induced variations of the surface resistance are determined, in the framework of the Coffey and Clem model, by taking into account the distribution of the vortex magnetic field inside the sample. It is shown that the effects of the critical state cannot generally be disregarded to account for the experimental data. Results obtained in bulk niobium at low temperatures are quantitatively justified.