Vortex mediated microwave absorption in superclean layered superconductors

TL;DR

This paper investigates vortex core excitations in superclean layered superconductors, predicting resonances and anomalies in microwave absorption related to vortex dynamics, supported by microscopic theory and experimental comparisons.

Contribution

It introduces a microscopic theory of vortex core excitations in superclean superconductors, predicting resonances and anomalies in microwave absorption.

Findings

Resonances at frequencies matching vortex excitation levels.

Even-odd anomaly in vortex excitation spectrum.

Absorption at very low frequencies linked to impurity-induced level crossings.

Abstract

In the superclean case the spectrum of vortex core excitations in the presence of disorder is not random but consists of two series of equally-spaced levels. The I-V characteristics of such superconductors displays many interesting phenomena. A series of resonances is predicted at frequencies commensurate with the spacing of the vortex excitations. These resonances reveal an even-odd anomaly. In the presence of one weak impurity the excitation levels can approach each other and almost cross. Absorption at very low frequencies is identified with the resonances arising in this case. The results of such microscopic theory coincide up to the order of magnitude with both the theory employing kinetic equation and the experiment. The non-linear effects associated with Zener transitions in such crossings are studied. These phenomena can be used as a probe of vortex core excitations.