NATURE OF PHASE-TRANSITIONS OF SUPERCONDUCTING WIRE NETWORKS IN A MAGNETIC-FIELD

We study I-V characteristics of periodic square Nb wire networks as a function of temperature in a transverse magnetic field, with a focus o n three fillings 2/5, 1/2, and 0.618 that represent very different lev els of incommensurability. For all three fillings, a scaling behavior of I-V characteristics is found, suggesting a finite temperature conti nuous superconducting phase transition. The low-temperature I-V charac teristics are found to have an exponential form, indicative of the dom ain-wall excitations.