In-plane vortex-lattice depinning in a layered superconductor

The out-of-plane (c-axis) dissipation of the layered superconductor ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CaCu}}_2$ ${\mathrm{O}}_8$ has been probed in the mixed state by current-voltage (I-V) measurements. Distinctly different behavior is observed for magnetic field H oriented parallel (?) and (⊥) to c, suggestive of two different out-of-plane dissipation mechanisms. We interpret our results for H⊥c as arising from Josephson vortex dynamics.