We have measured dissipation-induced localization of the reaction coordinate for a metastable-state decay process in a model system with moderate damping. Specifically, the supercurrent in an array of Tl2Ba2CaCu2O8 intrinsic Josephson junctions is larger when all the junctions are in the zero-voltage state than when one or more junctions are in the voltage state since the dissipation is larger in the former case.

We have fabricated intrinsic Josephson junction arrays in Tl 2 Ba 2 CaCu 2 O 8 thin films using three-dimensional focussed ion-beam milling. We have measured the dependence of the switching current density of these arrays at 4.2 K upon the junction cross-sectional area. There is strong suppression of the switching current density for junctions of area less than 1 m 2 , the current extrapolating to zero at an area of 0.25 m 2. We discuss the roles of gallium ion implantation and both thermal and quantum fluctuations in this current suppression.

We report current-voltage measurements on arrays of high-Tc intrinsic Josephson junctions showing a temperature dependence of the first critical current which is different from that of subsequent critical currents for an array with sub-micron dimensions. This can be explained by the change in the impedance seen by other array-junctions once one junction switches out of the supercurrent state, resulting in a switching-off of thermally activated phase-diffusion.

Abstract-We have fabricated intrinsic Josephson junction arrays using Tl 2 Ba 2 CaCu 2 O 8 thin films. The junctions have dimensions of order 1 m 2 and therefore high slope resistance in the range 1 k to 10 k per junction on the quasiparticle branches. We have irradiated the junctions with microwaves at a frequency of 6.37 GHz. We observe both microwave-induced vortex-flow branches and strong suppression of the switching current but only when no junctions are in the voltage state. We attribute this observation to the shunting of the high-resistance junctions by the environmental impedance, and discuss the significance of this result for the application of intrinsic junctions as THz sources and qubits.

We present experimental results on intrinsic Josephson junctions fabricated by three-dimensional gallium focussed-ion-beam (FIB) milling in c-axis-oriented Tl2Ba2CaCu2O8 thin films. We report measurements of the dependence of the switching current density of these arrays at 4.2 K upon the junction cross-sectional area A showing strong suppression of the switching current density for junctions with A 1 μm 2 ; the switching current extrapolates to zero for A ∼ 0.25 μm 2. We discuss the roles of gallium ion implantation and both thermal and quantum fluctuations in this current suppression. We also present in-situ IV measurements demonstrating the use of a liquid-helium-cooled sample stage in conjunction with the FIB milling.