Slowing down Josephson vortex lattice in Bi_2Sr_2CaCu_2O_{8+d} with pancake vortices

TL;DR

This paper investigates how pancake vortices influence the motion of Josephson vortex lattices in layered high-temperature superconductors, revealing a nonmonotonic damping effect modulated by magnetic fields, temperature, and irradiation.

Contribution

It provides a combined theoretical and experimental analysis of pancake vortex effects on Josephson vortex dynamics in Bi-2212 superconductors, highlighting the nonmonotonic damping behavior.

Findings

Pancake vortices strongly suppress Josephson vortex mobility.

Maximum damping occurs when Josephson frequency matches vortex relaxation frequency.

Heavy ion irradiation reduces pancake-vortex damping at low temperatures.

Abstract

We study theoretically and experimentally influence of pancake vortices on motion of the Josephson vortex lattice in layered high-temperature superconductors. Mobility of the Josephson vortices in layered superconductors is strongly suppressed by small amount of pancake-vortex stacks. Moving Josephson vortex lattice forces oscillating zigzag deformation of the pancake-vortex stacks contributing to damping. The salient feature of this contribution is its nonmonotonic dependence on the lattice velocity and the corresponding voltage. Maximum pancake effect is realized when the Josephson frequency matches the relaxation frequency of the stacks. The pancake-vortex damping is strongly suppressed by thermal fluctuations of the pancake vortices. This theoretical picture was qualitatively confirmed by experiments on two mesas prepared out of Bi_2Sr_2CaCu_2O_{8+d} whiskers. We found that the Josephson-vortex flux-flow voltage is very sensitive to small c-axis magnetic field. The pancake-vortex contribution to the current indeed nonmonotonically depends on voltage and decreases with increasing temperature and in-plane magnetic field. We also found that irradiation with heavy ions has no noticeable direct influence on motion of the Josephson vortices but dramatically reduces the pancake-vortex contribution to the damping of the Josephson vortex lattice at low temperatures.