Current distribution of collective thermal depinning of Josephson vortices in naturally stacked Josephson junctions

Abstract

We investigated the thermal-depinning current ͑I c ͒ distribution of Josephson vortices ͑JVs͒ in naturally stacked Bi 2 Sr 2 CaCu 2 O 8+␦ intrinsic Jospehson junctions in tesla-range magnetic fields and at different field tilt angles from the in-plane position. The I c distribution in the thermal-activation regime contains accurate information on the bias and magnetic-field dependence of the Josephson-vortex pinning potential. In a few-teslarange magnetic field, JVs in a row in a junction, strongly coupled with each other, are pinned or depinned like a single physical entity at a single pinning center. In the best-aligned in-plane magnetic field, the edge pinning is most relevant and is insensitive to the field strength. In the presence of pancake vortices ͑PVs͒ in a slightly tilted field, however, the PV pinning deepens the JV pinning potential linearly with the number of PVs.

Fluctuating pancake vortices revealed by dissipation of the Josephson vortex lattice

“…Comparing the field dependences (14) and (18), we see that in the narrow strips, the slope of the U min versus H z dependence should be smaller by the geometrical factor [1 − 1/ cosh (w/2λ)] < 1. Due to the temperature dependence of λ, we may expect to observe the crossover between these regimes for the strips with w λ(0) by varying the temperature.…”