Christina PSAROUDAKI
Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
We provide a comprehensive picture of the quantum propagation of skyrmions in
chiral magnets, focusing on the microscopic description of dissipation at zero and
finite temperatures, originating from the interaction of the skyrmion with quantum
fluctuations. The most interesting feature is that the effect of this damping is reduced
to a mass term that is predicted for the first time [1]. We demonstrate that a skyrmion
in a confined geometry behaves as a massive particle, a discovery with great impact
on the technologically important case of linear tracks relevant for magnetic memory
devices [1]. An additional quantum mass term is predicted with an explicit
temperature dependence which remains finite even at zero temperature.
In the presence of time-dependent oscillating magnetic field gradients, the
unavoidable coupling of the external field to the magnons gives rise to timedependent
dissipation for the skyrmion, with measurable consequences on the
skyrmion’s path [2]. These ac fields act as a net driving force on the skyrmion via its
own intrinsic magnetic excitations. We generalize the standard quantum theory of
dissipation to include the effects of the driven bath on the skyrmion dynamics. We
address the stochastic effects of the quantum driven bath on the skyrmion propagation
[3], and provide a generalized version of the nonequilibrium fluctuation-dissipation
relation for externally driven reservoirs.
Our work initiates studies towards the possibility of observing a quantum mechanical
behavior at a mesoscopic scale. I will briefly talk about the observability of tunneling
events, in particular quantum depinning of a magnetic skyrmion out of a pinning
center [4].
Skyrmions in Chiral Magnets, Phys. Rev. X 7, 041045 (2017).
[2] C. Psaroudaki and D. Loss, Skyrmions Driven by Intrinsic Magnons, Phys. Rev.
Lett. 120, 237203 (2018).
[3] C. Psaroudaki, P. Aseev, and D. Loss, "Quantum Brownian Motion of a Magnetic
Skyrmion", arXiv:1904.09215
[4] C. Psaroudaki and D. Loss, "Quantum Deppining of a Magnetic Skyrmion",
manuscript in preparation (2019).