Quantum Dynamics of Magnetic Skyrmions: Consistent Path Integral Formulation
Abstract
We present a path integral formalism for the intrinsic quantum dynamics of magnetic skyrmions coupled to a thermal background of magnetic fluctuations. Upon promoting the skyrmion's collective coordinate to a dynamic variable and integrating out the magnonic heat bath, we derive the generalized equation of motion for with a non-local damping term that describes a steady-state skyrmion dynamics at finite temperatures. Being essentially temperature dependent, the intrinsic damping is shown to originate from the coupling of thermally activated magnon modes to the adiabatic potential driven by a rigid skyrmion motion, which can be regarded as another manifestation of emergent electrodynamics inherent to topological magnetic textures. We further argue that the diagonal components of the damping term act as the source of dissipation and inertia, while its off-diagonal components modify the gyrotropic motion of a magnetic skyrmion. By means of numerical calculations for the lattice spin model of chiral ferromagnets, we study the temperature behavior of the intrinsic damping as a function of magnetic field in periodic and confined geometries. The intrinsic damping is demonstrated to be highly non-local, revealing its quantum-mechanical nature, that becomes more pronounced with increasing temperature. At high temperatures when the magnon occupation factors are large, the intrinsic damping is shown to yield a modified Thiele's equation with the additional non-local dissipative and mass terms that exhibit an almost linear temperature behavior. Our results provide a microscopic background for semiclassical magnetization dynamics and establish a framework for understanding spin caloritronics effects in topological magnetic textures.
Cite
@article{arxiv.2206.08532,
title = {Quantum Dynamics of Magnetic Skyrmions: Consistent Path Integral Formulation},
author = {Sergey A. Nikolaev and Akihiro Tanaka},
journal= {arXiv preprint arXiv:2206.08532},
year = {2022}
}
Comments
This preprint has been retracted by the authors with the intention of reshaping the contents into a more complete form. In particular, we have come to notice thanks to help from colleagues that our criticisms directed toward refs. 35-38 are largely unfounded. For this we apologize to the authors of those references. A substantially updated work will be posted to these arXiv's in the near future