Transverse Depinning and Melting of a Moving Vortex Lattice in Driven Periodic Josephson Junction Arrays

We study the effect of thermal fluctuations in a vortex lattice driven in the periodic pinning of a Josephson junction array. The phase diagram current ( $I$) vs temperature ( $T$) is studied. Above the critical current $I_c\left(T\right)$ we find a moving vortex lattice (MVL) with anisotropic Bragg peaks. For large currents $I\gg I_c\left(T\right)$, there is a melting transition of the MVL at $T_M\left(I\right)$. When applying a small transverse current to the MVL, there is negligible dissipation at low $T$. We find an onset of transverse vortex motion at a transverse depinning temperature $T_{\mathrm{tr}}\left(I\right)<T_M\left(I\right)$.