Skyrmion dynamics and transverse mobility: skyrmion Hall angle reversal on 2D periodic substrates with dc and biharmonic ac drives

Vizarim, N. P.; Reichhardt, C.; Venegas, P. A.

doi:10.1140/epjb/e2020-10135-1

Cited by 11 publications

(7 citation statements)

References 91 publications

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“…The impact of thermal fluctuations would be an interesting issue to address in a future study. It is known that temperature can modify phase transition points, or even cause them to vanish [46]. Thermal creep could also become relevant [41].…”

Section: Discussionmentioning

confidence: 99%

“…( 1) is the interaction between the skyrmion and the obstacles. We model this potential with the Gaussian form [10,11,46] U o = C o e −(rio/ao) 2 , where C o is the strength of the obstacle potential, r io is the distance between skyrmion i and obstacle o, and a o is the obstacle radius. Thus, the force between the obstacle and the skyrmion takes the form F o i = −∇U o = −F o r io e −(rio/ao) 2 r io , where F o = 2C o /a 2 o .…”

Section: Simulationmentioning

confidence: 99%

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Directional Locking and the Influence of Obstacle Density on Skyrmion Dynamics in Triangular and Honeycomb Arrays

Vizarim,

Souza,

Reichhardt

et al. 2021

Preprint

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We numerically examine the dynamics of a single skyrmion driven over triangular and honeycomb obstacle arrays at zero temperature. The skyrmion Hall angle θ sk , defined as the angle between the applied external drive and the direction of the skyrmion motion, increases in quantized steps or continuously as a function of the applied drive. For the obstacle arrays studied in this work, the skyrmion exhibits two main directional locking angles of θ sk = −30 • and −60 • . We show that these directions are privileged due to the obstacle landscape symmetry, and coincide with channels along which the skyrmion may move with few or no obstacle collisions. By changing the obstacle density, we can modify the skyrmion Hall angles and cause some dynamic phases to appear or grow while other phases vanish. This interesting behavior can be used to guide skyrmions along designated trajectories via regions with different obstacle densities. For fixed obstacle densities, we investigate the evolution of the locked θ sk = −30 • and −60 • phases as a function of the Magnus force, and discuss possibilities for switching between these phases using topological selection.

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Section: Discussionmentioning

confidence: 99%

Section: Simulationmentioning

confidence: 99%

Directional Locking and the Influence of Obstacle Density on Skyrmion Dynamics in Triangular and Honeycomb Arrays

Vizarim,

Souza,

Reichhardt

et al. 2021

Preprint

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show abstract

“…Recently, it was shown that the skyrmion Hall angle can be manipulated by introducing periodic pinning [34][35][36][37][38][39] . As the external drive is increased, the skyrmion Hall angle becomes quantized due to directional locking effects very similar to those found in superconducting vortices 40 or colloidal assemblies [41][42][43] driven over a periodic substrate under a rotating external drive.…”

Section: Introductionmentioning

confidence: 99%

Soliton motion in skyrmion chains: Stabilization and guidance by nanoengineered pinning

et al. 2022

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Using a particle-based model we examine the depinning motion of solitons in skyrmion chains in quasi-one dimensional (1D) and two-dimensional (2D) systems containing embedded 1D interfaces. The solitons take the form of a particle or hole in a commensurate chain of skyrmions. Under an applied drive, just above a critical depinning threshold the soliton moves with a skyrmion Hall angle of zero. For higher drives, the entire chain depins, and in a 2D system we observe that both the solitons and chain move at zero skyrmion Hall angle and then transition to a finite skyrmion Hall angle as the drive increases. In a 2D system with a 1D interface that is at an angle to the driving direction, there can be a reversal of the sign of the skyrmion Hall angle from positive to negative. Our results suggest that solitons in skyrmion systems could be used as information carriers in racetrack geometries that would avoid the drawbacks of finite skyrmion Hall angles. The soliton states become mobile at significantly lower drives than the depinning transition of the skyrmion chains themselves.

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“…For skyrmions interacting with a periodic array of pinning sites or obstacles under a dc drive, the skyrmion Hall angle is not constant but increases with increasing skyrmion velocity and exhibits a series of steps produced when the skyrmion motion locks to symmetry directions of the substrate, followed by a saturation at high velocities to the intrinsic or disorder free value [31][32][33]. When combined ac and dc driving is used to move skyrmions over a periodic pinning array, a variety of both directional locking and phase locking effects appear [34,35]. The phase locking effects resemble Shapiro steps in which the ac drive frequency matches with the intrinsic frequency of the motion of the skyrmion over the periodic substrate, leading to steps in the skyrmion velocity-force curves [36,37].…”

Section: Introductionmentioning

confidence: 99%

“…For ac parameters which place the skyrmion orbit at the boundary between two different stable commensurate orbits, the motion is chaotic and the skyrmion diffuses through the system. It is even possible in some cases to obtain directed skyrmion motion under purely ac driving by using a biharmonic or circular ac drive to induce a ratchet effect [34,40]. In studies of skyrmions interacting with periodic obstacle arrays, the directed motion has a fixed orientation if the ac drive amplitude and frequency is held fixed [40].…”

Section: Introductionmentioning

confidence: 99%

Guided Skyrmion Motion Along Pinning Array Interfaces

Vizarim,

Reichhardt,

Venegas

et al. 2020

Preprint

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We examine ac driven skyrmions interacting with the interface between two different obstacle array structures. We consider drive amplitudes at which skyrmions in a bulk obstacle lattice undergo only localized motion and show that when an obstacle lattice interface is introduced, directed skyrmion transport can occur along the interface. The skyrmions can be guided by a straight interface and can also turn corners to follow the interface. For a square obstacle lattice embedded in a square pinning array with a larger lattice constant, we find that skyrmions can undergo transport in all four primary symmetry directions under the same fixed ac drive. We map where localized or translating motion occurs as a function of the ac driving parameters. Our results suggest a new method for controlling skyrmion motion based on transport along obstacle lattice interfaces.

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Skyrmion dynamics and transverse mobility: skyrmion Hall angle reversal on 2D periodic substrates with dc and biharmonic ac drives

Cited by 11 publications

References 91 publications

Directional Locking and the Influence of Obstacle Density on Skyrmion Dynamics in Triangular and Honeycomb Arrays

Directional Locking and the Influence of Obstacle Density on Skyrmion Dynamics in Triangular and Honeycomb Arrays

Soliton motion in skyrmion chains: Stabilization and guidance by nanoengineered pinning

Guided Skyrmion Motion Along Pinning Array Interfaces

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