Analysis of current-voltage characteristics of two-dimensional superconductors: Finite-size scaling behavior in the vicinity of the Kosterlitz-Thouless transition

Abstract

It has been suggested [Pierson et al., Phys. Rev. B 60, 1309 (1999); Ammirata et al., Physica C 313, 225 (1999)] that for two-dimensional (2D) superconductors there exists a phase transition with the dynamic critical exponent z≈5.6. We perform simulations for the 2D resistively-shunted-junction model and compare the results with the experimental data in Repaci et al. obtained for an ultrathin YBCO sample [Phys. Rev. B 54, R9674 (1996)]. We then use a different method of analyzing dynamic scaling than in Pierson et al., and conclude that both the simulations and the experiments are consistent with a conventional Kosterlitz Thouless (KT) transition in the thermodynamic limit for which z=2. For finite systems, however, we find both in simulations and experiments that the change in the current-voltage (I−V) characteristics caused by the finite size shows a scaling property with an exponent α≈1/6, seemingly suggesting a vanishing resistance at a temperature for which z=α−1. It is pointed out that the dynamic critical exponent found in Pierson et al. corresponds to the exponent α−1. It is emphasized that this scaling property does not represent any true phase transition since in reality the resistance vanishes only at zero temperature. Nevertheless, the observed scaling behavior associated with α≈1/6 appears to be a common and intriguing feature for the finite size caused change in the I−V characteristics around the KT transition.

Source-reported materials — not catalogue approval

Similar papers