Magnetic-field dependence of ultrasonic attenuation in a granular superconductor

S. Sergeenkov; M. Ausloos

doi:10.1103/PhysRevB.46.14223

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Magnetic-field dependence of ultrasonic attenuation in a granular superconductor

S. Sergeenkov, M. Ausloos

DOI 10.1103/PhysRevB.46.14223 · Physical Review B

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Abstract

The magnetic-field, temperature, and frequency dependence of the ultrasonic attenuation due to phase fluctuations in a lattice of Josephson-coupled grains are considered within a model for a granular superconductor. The results obtained show a striking resemblance with the predictions and observations for ultrasonic attenuation by the vortex lattice fluctuations in the mixed state of type-II superconductors. The frequency dependence of the irreversibility line due to decoupling of grains is found to obey a power law, instead of a logarithmic one resulting from the flux-creep mechanism. It is argued that the weak-link-assisted ultrasonic attenuation mechanism is of importance at low fields (below the first Abrikosov critical field) in ceramics, and can essentially modify (via defect flux pinning) the thermally assisted flux flow dissipative mechanism in single crystals.