Fluctuating pancake vortices revealed by dissipation of Josephson vortex lattice

TL;DR

This paper investigates how fluctuating pancake vortices affect the dissipation of Josephson vortex lattices in layered superconductors, combining theoretical calculations with experimental measurements to reveal their influence.

Contribution

It provides the first detailed calculation of fluctuating pancake vortices' contribution to c-axis conductivity and confirms their presence through experimental data.

Findings

Exponential dependence of c-axis conductivity observed experimentally.

Strong evidence of fluctuating pancake vortices influencing vortex lattice dissipation.

Theoretical results match experimental measurements on Bi2212 small mesas.

Abstract

In strongly anisotropic layered superconductors in tilted magnetic fields the Josephson vortex lattice coexists with the lattice of pancake vortices. Due to the interaction between them, the dissipation of the Josephson-vortex lattice occurs to be very sensitive to the presence of the pancake vortices. If the c-axis magnetic field is smaller then the corresponding lower critical field, the pancake stacks are not formed but the individual pancakes may exist in the fluctuational regime either near surface in large-size samples or in the central region for small-size mesas. We calculate the contribution of such fluctuating pancake vortices to the c-axis conductivity of the Josephson vortex lattice and compare the theoretical results with measurements on small mesas fabricated out of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ crystals. A fingerprint of fluctuating pancakes is characteristic exponential dependence of the c-axis conductivity observed experimentally. Our results provide strong evidence of the existence of the fluctuating pancakes and their influence on the Josephson-vortex-lattice dissipation.