High sheet resistance Hg(Xe) films exhibit I - V characteristics of the form V ∼ Ia, in agreement with a model of current-induced vortex-antivortex unbinding. The detailed form of the vortex interaction is confirmed. Quantitative evidence is presented for a vortex unbinding transition of the Kosterlitz-Thouless universality class.
Bibliographical noteFunding Information:
The authorsw ish to thank V. Ambegaokar, E.D. DahlbergB, .I. Halperina nd D.R. Nelson for severaul sefuld iscussionsS.u pportw as provided by the NSF under grant NSF/DMR-8011948a nd by the GraduateS chool of the Universityo f Minnesota.