1ST-ORDER KOSTERLITZ-THOULESS PHASE-TRANSITION IN LAYERED HIGH-T(C) SUPERCONDUCTOR UNDER MAGNETIC INDUCTION

The influence of an external magnetic field, penetrating into the Josephson-decoupled layered superconductor as a flux line lattice, on the dissociation of the free two-dimensional vortex-antivortex dipoles is investigated. A sufficiently small critical value of the induction B(cr) as compared with the lower critical field H(cl) is obtained. At a small induction B < B(cr), the second-type phase transition occurs following the well-known Kosterlitz-Thouless scenario. The phase transition, which is normally of the second type, becomes of the first type at large induction B > B(cr). The pair dissociation exhibits a hysteretic behavior in some temperature interval up to the Kosterlitz-Thouless temperature T(KT). In this temperature interval the resistivity of the superconductors exhibits hysteretic behavior.