RESISTIVE TRANSITION IN SUPERCONDUCTING FILMS

The consequences of a vortex unbinding picture of two-dimensional superconductivity are worked out. Although there is no true finite-temperature phase transition, dirty superconducting films should display anomalous behavior below the BCS transition temperature and above an effective Kosterlitz-Thouless vortex unbinding temperature. In particular, both the conductivity and fluctuation diamagnetism behave like ξ+2in this regime, where ξ+ is the correlation length calculated by Kosterlitz, ξ+∼ξc exp (B/T - Tc)1/2. We estimate ξc, B, and the vortex unbinding temperature, and determine the nonlinear resistivity below Tc. A recent theory of vortex dynamics, together with a time-dependent Ginzburg-Landau theory, lead to a determination of the frequency-dependent conductivity. © 1979 Plenum Publishing Corporation.