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Title: Reversible vector ratchets for skyrmion systems

Abstract

In this paper, we show that ac driven skyrmions interacting with an asymmetric substrate provide a realization of a class of ratchet system which we call a vector ratchet that arises due to the effect of the Magnus term on the skyrmion dynamics. In a vector ratchet, the dc motion induced by the ac drive can be described as a vector that can be rotated clockwise or counterclockwise relative to the substrate asymmetry direction. Up to a full 360° rotation is possible for varied ac amplitudes or skyrmion densities. In contrast to overdamped systems, in which ratchet motion is always parallel to the substrate asymmetry direction, vector ratchets allow the ratchet motion to be in any direction relative to the substrate asymmetry. It is also possible to obtain a reversal in the direction of rotation of the vector ratchet, permitting the creation of a reversible vector ratchet. We examine vector ratchets for ac drives applied parallel or perpendicular to the substrate asymmetry direction, and show that reverse ratchet motion can be produced by collective effects. No reversals occur for an isolated skyrmion on an asymmetric substrate. Finally, since a vector ratchet can produce motion in any direction, it could representmore » a method for controlling skyrmion motion for spintronic applications.« less

Authors:
 [1]; ORCiD logo [2];  [2]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of Notre Dame, IN (United States)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1356134
Alternate Identifier(s):
OSTI ID: 1345685
Report Number(s):
LA-UR-16-27322
Journal ID: ISSN 2469-9950; TRN: US1702609
Grant/Contract Number:
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 95; Journal Issue: 10; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 36 MATERIALS SCIENCE; Material Science

Citation Formats

Ma, Xiu, Reichhardt, Cynthia Jane Olson, and Reichhardt, Charles. Reversible vector ratchets for skyrmion systems. United States: N. p., 2017. Web. doi:10.1103/PhysRevB.95.104401.
Ma, Xiu, Reichhardt, Cynthia Jane Olson, & Reichhardt, Charles. Reversible vector ratchets for skyrmion systems. United States. doi:10.1103/PhysRevB.95.104401.
Ma, Xiu, Reichhardt, Cynthia Jane Olson, and Reichhardt, Charles. Fri . "Reversible vector ratchets for skyrmion systems". United States. doi:10.1103/PhysRevB.95.104401. https://www.osti.gov/servlets/purl/1356134.
@article{osti_1356134,
title = {Reversible vector ratchets for skyrmion systems},
author = {Ma, Xiu and Reichhardt, Cynthia Jane Olson and Reichhardt, Charles},
abstractNote = {In this paper, we show that ac driven skyrmions interacting with an asymmetric substrate provide a realization of a class of ratchet system which we call a vector ratchet that arises due to the effect of the Magnus term on the skyrmion dynamics. In a vector ratchet, the dc motion induced by the ac drive can be described as a vector that can be rotated clockwise or counterclockwise relative to the substrate asymmetry direction. Up to a full 360° rotation is possible for varied ac amplitudes or skyrmion densities. In contrast to overdamped systems, in which ratchet motion is always parallel to the substrate asymmetry direction, vector ratchets allow the ratchet motion to be in any direction relative to the substrate asymmetry. It is also possible to obtain a reversal in the direction of rotation of the vector ratchet, permitting the creation of a reversible vector ratchet. We examine vector ratchets for ac drives applied parallel or perpendicular to the substrate asymmetry direction, and show that reverse ratchet motion can be produced by collective effects. No reversals occur for an isolated skyrmion on an asymmetric substrate. Finally, since a vector ratchet can produce motion in any direction, it could represent a method for controlling skyrmion motion for spintronic applications.},
doi = {10.1103/PhysRevB.95.104401},
journal = {Physical Review B},
number = 10,
volume = 95,
place = {United States},
year = {Fri Mar 03 00:00:00 EST 2017},
month = {Fri Mar 03 00:00:00 EST 2017}
}

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  • Cited by 4
  • We present an analytical study of the response of cold atoms in an optical lattice to a weak time- and space-asymmetric periodic driving signal. In the noninteracting limit, and for a finite set of resonant frequencies, we show how a coherent, long-lasting ratchet current results from the interference between first- and second-order processes. In those cases, a suitable three-level model can account for the entire dynamics, yielding surprisingly good agreement with numerically exact results for weak and moderately strong driving.
  • It is shown how the Skyrme and the non-Skyrme terms arise naturally from an effective chiral Lagrangian with the vector and scalar mesons. Some errors in the literature concerning the use of the Skyrme and the non-Skyrme terms are pointed out.
  • Mattis has derived six relations among the partial-wave amplitudes for the reaction ..pi..N..-->..pN. From these relations we deduce that the six independent helicity amplitudes for the t-channel isospin-zero reaction may be simply expressed in terms of one unknown function. This leads to definite predictions for the rho-meson density matrix and the absence of nucleon polarization effects, which can be tested directly, without recourse to partial-wave analysis.
  • We consider classical static Skyrmion-anti-Skyrmion and Skyrmion-Skyrmion configurations, symmetric with respect to a reflection plane, or symmetric up to a G-parity transformation, respectively. We show that the stress tensor component completely normal to the reflection plane, and hence its integral over the plane, is negative definite or positive definite, respectively. Classical Skyrmions always repel classical Skyrmions and classical Skyrmions always attract classical anti-Skyrmions and thus no static equilibrium, whether stable or unstable, is possible in either case. No other symmetry assumption is made and so our results also apply to multi-Skyrmion configurations. Our results are consistent with existing analyses ofmore » Skyrmion forces at large separation, and with numerical results on Skymion-anti-Skyrmion configurations in the literature which admit a different reflection symmetry. They also hold for the massive Skyrme model. We also point out that reflection symmetric self-gravitating Skyrmions or black holes with Skyrmion hair cannot rest in symmetric equilibrium with self-gravitating anti-Skyrmions.« less