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

Abstract

By using thermal and Lorentz force, the vortex motion is successfully manipulated in the mixed state of underdoped ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}\mathrm{Cu}{\mathrm{O}}_{4}$ single crystals and optimally doped $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ 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 $(H\ensuremath{\Vert}c)$ 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.