Mixed-State Dissipation in Zero Temperature Limit in MgB2 Thin Films
Abstract
We have studied mixed-state dissipation in epitaxial MgB2 thin films by measurements of resistive transition, current-voltage characteristics, Hall effect, and point-contact tunnelling spectrum. We found that unlike single gap superconductors with negligible vortex quantum fluctuations in which vortices are frozen at T=0 K, finite zero-temperature dissipation due to vortex motion exists in MgB2 over a wide magnetic field range. This dissipation was found to be associated with proliferation of quasiparticles from the π-band of MgB2. The result shows that the vortex fluctuations are enhanced by two-band superconductivity in MgB2 and we suggest that the vortex quantum fluctuation is a possible cause of the non-vanishing zero-temperature dissipation.
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