Manipulating vortex motion by thermal and Lorentz force in high temperature superconductors

TL;DR

This study demonstrates manipulation of vortex motion via thermal and Lorentz forces in high-temperature superconductors, revealing distinct vortex behaviors below and above the critical temperature through Nernst signal measurements.

Contribution

It introduces a new measurement configuration to distinguish vortex-related signals in the pseudogap region and clarifies vortex dynamics across the superconducting transition.

Findings

Strong Nernst signal above T_c is due to vortex motion.

In-plane Nernst signal persists up to high temperatures in the pseudogap region.

Dissipation mechanisms differ below and above T_c, involving Abrikosov vortices and vortex-antivortex pairs.

Abstract

By using thermal and Lorentz force, the vortex motion is successfully manipulated in the mixed state of underdoped La$_{2 - x}$Sr$_{x}$CuO$_{4}$ single crystals and optimally doped YBa$_{2}$Cu$_{3}$O$_{7 - \delta}$ thin films. A conclusion is drawn that the strong Nernst signal above $T_{c}$ is induced by vortex motion. In the normal state, in order to reduce the dissipative contribution from the quasiparticle scattering and enhance the signal due to the possible vortex motion, a new measurement configuration is proposed. It is found that the in-plane Nernst signal ($H$ $| | $ $c$) can be measurable up to a high temperature in the pseudogap region, while the Abrikosov flux flow dissipation can only be measured up to $T_{c}$. This may point to different vortices below and above $T_{c}$ if we attribute the strong Nernst signal in the pseudogap region to the vortex motion. Below $T_{c}$ the dissipation is induced by the motion of the Abrikosov vortices. Above $T_{c}$ the dissipation may be caused by the motion of the spontaneously generated unbinded vortex-antivortex pairs.