Critical behavior of dynamic vortex Mott transition in superconducting arrays at fractional vortex densities

We study the differential resistivity transition of two-dimensional superconducting arrays induced by an external driving current, in the presence of thermal fluctuations and a magnetic field corresponding to $f$ flux quantum per plaquette. Recent experiments have identified this transition as a dynamic vortex Mott insulator transition at vortex densities near rational values of $f$. The critical behavior is determined from a scaling analysis of the current-voltage relation near the transition, obtained by Monte Carlo simulations of a Josephson-junction array model in the vortex representation. For a square-lattice array, the critical exponents obtained near $f=1/2$ are consistent with the experimental observations. The same scaling behavior is observed near $f=1/3$. For a honeycomb array, although similar results are obtained for $f=1/3$, the transition is absent for $f=1/2$, consistent with an incommensurate vortex phase.