VORTEX PAIR PRODUCTION AND DECAY OF A 2-DIMENSIONAL SUPERCURRENT BY AQUANTUM-FIELD-THEORY APPROACH

We investigate the phenomenon of the decay of a supercurrent through h omogeneous nucleation of vortex-antivortex pairs in a two-dimensional- tao like superconductor or superfluid by means of a quantum electrodyn amic formulation for the decay of the 2D vacuum. The case in which bot h externally driven current and Magnus force are present is treated ex actly, taking the vortex activation energy and its inertial mass as in dependent parameters. Quantum dissipation is included through the form ulation introduced by Caldeira and Leggett. The most relevant conseque nce of quantum dissipation is the elimination of the threshold for vor tex production due to the Magnus force. In the dissipation-dominated c ase, corresponding formally to the limit of sere inertial mass, an exa ct formula for the pair-production rate is given. If however the inert ial mass is strictly zero we find that vortex production is inhibited by a quantum effect related to the Magnus force. The possibility of in cluding vortex pinning is investigated by means of an effective harmon ic potential. While an additional term in the vortex activation energy can account for the effect of a finite barrier in the direction perpe ndicular to the current, pinning along the current depresses the role of the Magnus force in the dissipation-dominated dynamics, except for the above-mentioned quantum effect. A possible description of vortex n ucleation due to the combined effects of temperature and externally dr iven currents is also presented along with an evaluation of the result ing voltage drop.