Narrow Results

A novel Kosterlitz–Thouless phase and continuous melting transitions are proposed for Josephson vortex systems induced in layered superconductors by strong parallel magnetic fields. The mechanism of the phenomenon is revealed and the phase diagram with a multicritical point is presented.

We performed simulations on in-plane current driven Josephson vortex systems in high-T_c cuprates at weak parallel magnetic fields and /or low anisotropies. It is found that the in-plane resistivity is Lorentz-force dependent at small current regime below the melting transition. As the current increases, the Josephson vortex lattice melts dynamically, the Lorentz-force independence of resistivity reappears. These results are possibly related to the experiments on YBCO.

When a magnetic field is applied parallel to the superconducting layers in high-T_c superconductors (HTSCs), vortices become Josphson vortices (JVs). To study the magnetic phase diagram of JVs in strongly anisotropic HTSCs, we propose that the JV flow-resistance measurement is a powerful probe to observe periodic oscillations in the JV flow-resistance against the magnetic field. We could determine the magnetic phase diagram of JVs in Bi-2212, in which there exist a three-dimensionally-ordered state and a two-dimensionally quasi-ordered one.