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Strong quantum fluctuation of vortices in the new superconductor $MgB_2$

H. H. Wen·S. L. Li·Z. W. Zhao·Y. M. Ni·Z. A. Ren·G. C. Che·H. P. Yang·Z. Y. Liu·Z. X. Zhao
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Abstract

By using transport and magnetic measurement, the upper critical field $H_{c2}(T)$ and the irreversibility line $H_{irr}(T)$ has been determined. A big separation between $H_{c2}(0)$ and $H_{irr}(0)$ has been found showing the existence of a quantum vortex liquid state induced by quantum fluctuation of vortices in the new superconductor $MgB_2$. Further investigation on the magnetic relaxation shows that both the quantum tunneling and the thermally activated flux creep weakly depends on temperature. But when the melting field $H_{irr}$ is approached, a drastic rising of the relaxation rate is observed. This may imply that the melting of the vortex matter at a finite temperature is also induced by the quantum fluctuation of vortices.

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H. H. Wen, S. L. Li, Z. W. Zhao, Y. M. Ni, Z. A. Ren, G. C. Che, H. P. Yang, Z. Y. Liu, Z. X. Zhao. 2001-03-11. Strong quantum fluctuation of vortices in the new superconductor $MgB_2$. https://doi.org/10.1088/0256-307x%2F18%2F6%2F335

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