%0 Journal Article
%T Strong quantum fluctuation of vortices in the new superconductor $MgB_2$
%A H. H. Wen
%A S. L. Li
%A Z. W. Zhao
%A Y. M. Ni
%A Z. A. Ren
%A G. C. Che
%A H. P. Yang
%A Z. Y. Liu
%A Z. X. Zhao
%J Physics
%D 2001
%I arXiv
%R 10.1088/0256-307X/18/6/335
%X 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.
%U http://arxiv.org/abs/cond-mat/0102436v3