Scaling behavior of the crossover to short-stack regimes of Josephson vortex lattices in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ stacks

TL;DR

This study investigates how Josephson vortex lattice behavior in Bi2212 stacks transitions from bulk to surface-dominated interactions as magnetic field, junction size, and anisotropy change, revealing a crossover in vortex lattice structure.

Contribution

It provides a systematic analysis of the crossover from bulk to surface effects in Josephson vortex lattices, highlighting the scaling with junction length and anisotropy.

Findings

Oscillation period changes from φ₀/2 to doubled period with increasing magnetic field.

Crossover scales with junction length and anisotropy parameter.

Higher magnetic fields favor in-phase square vortex lattices in smaller, more anisotropic samples.

Abstract

We report the systematic investigations of the oscillation of the Josephson vortex (JV) flow resistance in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ micro-fabricated junctions with various geometries and superconducting anisotropy parameters. As the applied magnetic field parallel to the $ab$-plane is increased, oscillation with a period corresponding to a $\phi_0/2$ par atomic Josephson junction changes to oscillation with a doubled period. This crossover is scaled by both the junction length and the anisotropy parameter, indicating that the bulk inductive coupling that favors the triangular JV lattice is replaced with the surface deformation energy as the dominant interaction for a JV lattice. These results suggest that the in-phase square JV lattice is pronounced at a higher magnetic field in a smaller and more anisotropic sample.