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.
@article{arxiv.cond-mat/0703637,
title = {Mixed-State Dissipation in Zero Temperature Limit in $MgB_2$ Thin Films},
author = {Y. Jia and Y. Huang and H. Yang and L. Shan and C. Ren and C. G. Zhuang and Y. Cui and Qi Li and Z. K. Liu and X. X. Xi and H. H. Wen},
journal= {arXiv preprint arXiv:cond-mat/0703637},
year = {2007}
}