Kosterlitz-Thouless signatures from 3D vortex loops in layered superconductors

Abstract

Layered 3D high-Tc superconductors exhibit Kosterlitz-Thouless (KT)-like quasi-2D signatures, and a decoupling of layers for T>Tc has been suggested. A vortex-loop scaling approach to the layered 3D XY model, with bare anisotropic coupling ratio γ0−2≡scrI⊥/scrI∥, shows layer fluctuations are indeed effectively decoupled,but only at finite scales a≲r0∼γ0≫1, where rectangular loops cutting single layers dominate. Finite-scale KT-like unbinding at ‘‘TKT’’ (γ0)≲Tc(γ0) yields quasi-2D signatures outside a 3D critical region ‖(T-Tc)/Tc‖≡‖ɛ‖=‖ɛc‖<γ0−1/ν, where multilayer, elliptical tumbling loops dominate, correlated over scales ξ∼‖ɛ‖−ν≫r0.

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