VORTICES IN LAYERED HIGH-TC SUPERCONDUCTORS

We investigate the properties of a point-like vortex, vortex-antivortex pairs and vortex lines in layered superconductors. The formation energy of a single point-like vortex turns out to diverge logarithmically with the size of the sample. The spontaneous creation of vortex-antivortex pairs leads to a Kosterlitz-Thouless transition (at a temperature T(KT)) that is similar to the transition in 2D superconductors. The interaction between pairs in different planes is small. A single straight vortex line and a vortex line pair have the same energy as in continuous superconductors. However, the stiffness of a single vortex line in a layered superconductor is considerably smaller than in conventional systems, and the line "melts" in the absence of pinning at T(KT).