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Heterogeneous vortex dynamics in high temperature superconductors

Abstract : In high temperature superconductors with strong pinning, the change in shear properties of the vortex system is a plausible mechanism for the vanishing of the linear electrical resistance at the transition from vortex liquid to vortex solid. The divergence of the shear viscosity of the vortex liquid upon cooling is, in this respect, an ominent sign of a phase transition to an ensemble of localized vortices. By introducing a channel-confined structure on macroscopic defect-free $Bi_{2}Sr_{2}CaCu_{2}O_{8}$ single crystals using heavy ion irradiation, we have succeeded in probing the shear viscosity of the vortex liquid directly. Magneto-optical imaging shows that 20 $\mu$m wide pin-free channels separated by 20 $\mu$m wide strongly pinning walls were made successfully. The vortex liquid shear viscosity was then obtained from transport measurements. Contrary to previous studies, the present work focuses on very low magnetic fields, of the order of hundreds of Gauss. The vortex liquid shear viscosity, even in low fields, can be equally well fitted by the Nelson-Halperin theory for the dislocation density in a two-dimensional vortex fluid as by the power laws derived in the framework of vortex glass models. This result shows that the vortex ensemble in the confined medium behaves as a system of rectilinear lines, with edge dislocations threading the system from end to end. The progressive jamming of the vortex ensemble upon cooling mimics a vortex liquid to vortex glass transition. This finds an analogy with recently reported shear-induced solid-to-fluid transitions in soft glassy materials.
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Contributor : Feng Yang <>
Submitted on : Friday, March 26, 2010 - 3:50:11 PM
Last modification on : Friday, July 31, 2020 - 9:24:06 AM
Long-term archiving on: : Monday, June 28, 2010 - 4:48:13 PM

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  • HAL Id : tel-00467466, version 1

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Feng Yang. Heterogeneous vortex dynamics in high temperature superconductors. Superconductivity [cond-mat.supr-con]. Ecole Polytechnique X, 2009. English. ⟨tel-00467466⟩

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