Interlayer Critical Current in the Vortex State of Bi2Sr2CaCu2O8+δ Intrinsic Junctions

We measure the current-voltage (I–V) characteristics of the Bi₂Sr₂CaCu₂O_8+δ intrinsic Josephson junctions in the magnetic field parallel to the c-axis. In the liquid phase of vortices, the I–V curve reveals three stages: ohmic relation at low currents, rapid resistive transition and a quasiparticle branch. If the maximum Josephson current I_c is defined at the transition, its field dependence is in quantitative agreement with the recent measurements on the Josephson plasma frequency ω_p. This leads to the conclusion that both I_c and ω_p equivalently give the information for the interlayer phase coherence. In spite of the finite Josephson current, there appears Lorentz-force-independent dissipation at small currents, indicating that the interlayer critical current is zero in the liquid phase. We discuss the applicability of the phase-slip mechanism associated with the in-plane motion of the vortex pancakes.