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Phase diagram of randomly pinned vortex matter in layered superconductors: Dependence on the details of the point pinning

Dasgupta, Chandan and Valls, Oriol T (2007) Phase diagram of randomly pinned vortex matter in layered superconductors: Dependence on the details of the point pinning. In: Physical Review B, 76 . 184509-1-184509-12.

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We study the thermodynamic and structural properties of the superconducting vortex system in hightemperature layered superconductors, with magnetic field normal to the layers, in the presence of a small concentration of strong random point pinning defects via numerical minimization of a model free-energy functional in terms of the time-averaged local density of pancake vortices. Working at constant magnetic induction and point pinning center concentration, we find that the equilibrium phase at low temperature $(T)$ and small pinning strength $(s)$ is a topologically ordered Bragg glass. As $T$ or s is increased, the Bragg glass undergoes a first-order transition to a disordered phase which we characterize as a “vortex slush” with polycrystalline structure within the layers and interlayer correlations extending to about 20 layers. This is in contrast with the pinned vortex liquid phase into which the Bragg glass was found to melt, using the same methods, in the case of a large concentration of weak pinning centers: That phase was amorphous with very little interlayer correlation. The value of the second moment of the random pinning potential at which the Bragg glass melts for a fixed temperature is very different in the two systems. These results imply that the effects of random point pinning cannot be described only in terms of the second moment of the pinning potential and that some of the unresolved contradictions in the literature concerning the nature of the low $T$ and high $s$ phase in this system are likely to arise from differences in the nature of the pinning in different samples, or from assumptions made about the pinning potential.

Item Type: Journal Article
Publication: Physical Review B
Publisher: The American Physcial Society
Additional Information: Copyright of this article belongs to The American Physcial Society.
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 03 Jun 2008
Last Modified: 19 Sep 2010 04:45
URI: http://eprints.iisc.ac.in/id/eprint/14148

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