Non-resonant microwave and RF absorption insights into superconducting state of HTSC

Abstract

The magnetic field dependent dissipative processes in the mixed state of HTSC give rise to intense, low field signals when studied using continuous wave electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectrometers. The combination of field modulation and phase sensitive detection commonly used in these spectrometers provides a highly sensitive technique of measuring the field derivative of the power absorbed, dP/dH, by the sample. The technique can be used to detect superconductivity in miniscule amounts of a sample, to determine the quality of a given superconducting material and also to obtain useful insights into its mixed state. We shall illustrate the applications of the technique through our recent results on (1) non-resonant microwave absorption by intrinsc Josephson junctions and (2) non-resonant rf absorption signatures of reentrant melting line, in single crystals of BiSr₂CaCu₂O₈.