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Effect of fluctuations on vortex lattice structural transitions in superconductors

A. Gurevich·V. G. Kogan
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Abstract

The rhombic-to-square transition field $H_{\Box}(T)$ for cubic and tetragonal materials in fields along [001] is evaluated using the nonlocal London theory with account of thermal vortex fluctuations. Unlike extended Ginzburg-Landau models, our approach shows that the line $H_{\Box}(T)$ and the upper critical field $H_{c2}(T)$ do not cross due to strong fluctuations near $H_{c2}(T)$ which suppress the square anisotropy induced by the nonlocality. In increasing fields, this causes re-entrance of the rhombic structure in agreement with recent neutron scattering data on borocarbides.

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A. Gurevich, V. G. Kogan. 2001-06-05. Effect of fluctuations on vortex lattice structural transitions in superconductors. https://doi.org/10.1103/physrevlett.87.177009

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