Dynamics and nonmonotonic drag for individually driven skyrmions

Journal Article · 24 August 2021 · Physical Review. B

DOI: https://doi.org/10.1103/physrevb.104.064441 · OSTI ID:1873338

Reichhardt, Charles  ^[1]; Reichhardt, Cynthia Jane  ^[1]

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1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Here, we examine the motion of an individual skyrmion driven through an assembly of other skyrmions in the absence of quenched disorder. The skyrmion behavior is determined by the ratio of the damping and Magnus terms, known as the intrinsic skyrmion Hall angle. For fixed drive in the damping dominated regime, the effective viscosity decreases monotonically with increasing skyrmion density. In contrast, in the Magnus dominated regime, the velocity varies nonmonotonically with density, and there is a regime in which the skyrmion moves faster with increasing density, as well as a pronounced speed-up effect in which a skyrmion traveling through a dense medium moves more rapidly than for low densities or the single-particle limit. The velocity-force curves in the Magnus-dominated regime exhibit an overshoot effect and other differences from the damping-dominated regime. We find a finite threshold force for skyrmion motion which increases with density as well as a drive-dependent skyrmion Hall angle. We map dynamic phase diagrams showing the threshold for motion, nonlinear flow, speed-up, and saturation regimes. In some cases, increasing the density can reduce the skyrmion Hall angle while producing a velocity boost, which could be valuable for applications.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: 89233218CNA000001
• OSTI ID: 1873338
• Report Number(s): LA-UR-21-25393
• Journal Information: Physical Review. B, Journal Name: Physical Review. B Journal Issue: 6 Vol. 104; ISSN 2469-9950
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English