[PC6] Vortex, Nickelates

10:30 AM - 10:45 AM JST(1:30 AM - 1:45 AM UTC)

[PC6-04] Nonequilibrium Dynamics of Topological Defects in Type-II Superconductors

*Takuma Kanakubo¹, Taira Kawamura², Yusuke Kato^1,3 (1. Department of Physics, The University of Toky (Japan), 2. College of Science and Technology, Nihon University (Japan), 3. Department of Basic Science, The University of Tokyo (Japan))

Keywords:

Vortex,Topological defects,Nonequilibrium,Time-dependent Ginzburg-Landau theory

Topological defects in type-II superconductors behave as topologically protected stable objects, and their nonequilibrium dynamics are crucial for understanding the transport properties of superconductors, such as the flux-flow state. From this perspective, establishing methods to control the motion of topological defects in nonequilibrium states is an important issue in both condensed matter physics and applied research. To this end, we have theoretically studied the dynamics of phase defects under thermal and spin currents [1].At ISS2024, we demonstrated our analysis of the motion of superconducting quantum vortices under a temperature gradient, based on a theoretical model consisting of the time-dependent Ginzburg–Landau (TDGL) equation, Ampère’s law, and the heat diffusion equation [1]. There, we derived an analytical expression for the vortex velocity and showed that vortices move toward the higher-temperature region. This motion can be understood as a process in which vortices gain energy by being attracted to the region of suppressed order parameter, providing an intuitive picture analogous to vortex pinning. However, a fundamental limitation of the conventional TDGL equation is the absence of contributions from nonequilibrium quasiparticles responsible for heat transport phenomena.In the present study, to overcome this limitation, we introduce a coupled system of equations consisting of an extended TDGL equation incorporating quasiparticle nonequilibrium and the kinetic equation for the nonequilibrium distribution function [2–5]. We focus on the nonequilibrium dynamics of topological defects (domain walls) in which physical quantities vary spatially along a single direction. From the extended TDGL equation, we derive a local momentum-balance relation, which enables quantitative evaluation of the force acting on the phase defect. On the other hand, the kinetic equation for the nonequilibrium distribution function is derived from the Usadel equation obeyed by quasiclassical Green’s functions in the dirty limit, and it is shown to be equivalent to a local energy-balance relation. References[1] T. Kanakubo et al., arXiv:2405.10200.[2] L. P. Gor’kov and G. M. Eliashberg, Sov. Phys. JETP 27, 328 (1968).[3] L. Kramer and R. J. Watts-Tobin, Phys. Rev. Lett. 40, 1041 (1978).[4] R. J. Watts-Tobin et al., J. Low Temp. Phys. 42, 459 (1981).[5] D. Y. Vodolazov and F. M. Peeters, Phys. Rev. B 81, 184521 (2010).