EVIDENCE FOR NONCONVENTIONAL VORTEX DYNAMICS IN AN IDEAL 2-DIMENSIONAL SUPERCONDUCTOR

Impedance measurements performed on a weakly frustrated triangular arr ay of Josephson junctions over a wide range of frequencies and at temp eratures such that vortex pinning is irrelevant reveal that vortex dyn amics in an ideal two-dimensional (2D) superconductor does not obey Dr ude's classical prediction for a 2D Coulomb gas of free and independen t vortex charges. An analysis in terms of a complex vortex dielectric constant implies that the vortex mobility vanishes logarithmically in the limit of small frequencies, thereby pointing to anomalous vortex d iffusion.