Vortex phases and dissipation in high-temperature superconducting oxides

Abstract

An (H,T) phase diagram is proposed to illustrate various vortex phases in the high-temperature superconducting oxides. Two types of vortices (thermally and magnetic field induced) are studied phenomenologically as a function of the temperature (T), magnetic field (H,H∥c axis), and current density (J). It is concluded that the quasi-two-dimensional nature of the high-temperature superconductors results in a ‘‘vortex plasma’’ phase above Hc1 and below a crossover field Hx. Between Hx and Hc2 and for T<TM, where TM is the two-dimensional melting temperature, the superconductors are in the flux-solid phase. The irreversible line Tirr(H) is attributed to the melting of a flux-solid to a flux-liquid phase. Dissipation occurs in the flux-liquid phase, and the (H,T) dependence of the dissipation is determined by the pinning mechanism. Above TKT and below Tc0, flux entanglement may take place near Hc1, and the ‘‘entangled-flux-liquid phase’’ proposed by Nelson is compatible with the flux-liquid phase near Hc2. The proposed phase diagram provides a consistent picture for the experimental results in both YBa2Cu3O7 and Bi2.2Sr2Ca0.8Cu2O8 single crystals.

Source-reported materials — not catalogue approval

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