Dissipation in the superconducting state of {kappa}-(BEDT-TTF){sub 2}Cu(NCS){sub 2}.

We have studied the interlayer resistivity of the prototypical quasi-two-dimensional organic superconductor $\ensuremath{\kappa}\text{\ensuremath{-}}{(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF})}_{2}\mathrm{Cu}{(\mathrm{N}\mathrm{C}\mathrm{S})}_{2}$ as a function of temperature, current, and magnetic field, within the superconducting state. We find a region of nonzero resistivity whose properties are strongly dependent on magnetic field and current density. There is a crossover to non-Ohmic conduction below a temperature that coincides with the two-dimensional vortex solid\char21{}vortex liquid transition. We interpret the behavior in terms of a model of current- and thermally driven phase slips caused by the diffusive motion of the pancake vortices which are weakly coupled in adjacent layers, giving rise to a finite interlayer resistance.