TWO-DIMENSIONAL BEHAVIOUR OF LAYERED HIGH-Tc SUPERCONDUCTORS

Abstract

High-T c superconductors (HTSs) have a layered structure, which strongly affects their physics. Bulk crystals exhibit the two-dimensional (2D) behaviour typical for superconducting films of atomic thickness. Fluctuation contribution to conductivity above mean-field critical temperature T c0 is characteristic to 2D superconductors. Finite resistivity in layered HTSs appears above Berezinskii-Kosterlitz-Thouless (BKT) transition T c , which is by several degrees smaller than T c0 . Below T c power-law I-V curves are observed. The transition and its main manifestations are described as a result of thermal creation of 2D-vortices with cores residing inside single superconducting layers. Magnetoresistive effects near the BKT transition are discussed briefly.