Vortex-lattice melting, phase slips, and decoupling studied by microwave dissipation in Bi2Sr2CaCu2O8+δ

We have measured the microwave dissipation at 10 GHz in a Bi2Sr2CaCu2O8+delta single crystal, between 75 and 50 K, as a function of the static magnetic field applied parallel to the c axis. We observe a clear-cut onset in the dissipation precisely at the melting field. In the liquid phase, for fields ~1-2 kG, the in-plane and the c axis resistivities deduced from microwave absorption display a different temperature behavior, in contrast with dc measurements. Our c-axis high-frequency data and the dc results can be reconciled by including phase slips due to the motion of pancake vortices, as suggested by Koshelev. The microscopic origin of the c-axis dissipation is thus identified through its frequency dependence.