Suppression of broadband noise at mode locking in driven vortex matter

Okuma, S.; Inoue, Jun‐ichi; Kokubo, N.

doi:10.1103/physrevb.76.172503

Cited by 51 publications

(50 citation statements)

References 29 publications

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“…We observe similar sets of dynamical orderdisorder transitions between step and non-step regions for increasing F dc and find similar effects for ac driving in the x-direction. Studies in overdamped systems of collections of interacting vortices also show that the vortices are more ordered and exhibit suppressed noise fluctuations in a phase locked region 23,25 . At higher F dc , the effectiveness of the substrate gradually diminishes, the phase locking steps disappear, and the skyrmions can re- The n = 1 phase locked step at F dc = 0.25 from the point labeled a in Fig.…”

Section: Collective Effectsmentioning

confidence: 99%

“…Here, the effective elastic coupling between the particles comprising the lattice generates an intrinsic washboard frequency that can lock to the applied ac driving frequency. Such steps have been studied for vortices moving over random disorder [21][22][23][24][25] or through confined channel geometries 26 . For particles confined to 2D and moving over a quasi-1D substrate, both the ac and dc drives must be applied in the same direction to produce Shapiro steps; however, for vortices moving over 2D periodic or egg-carton substrates, it is possible to obtain what are called transverse phase locking steps when the ac drive is perpendicular to the direction of the dc drive [27][28][29] .…”

Section: Introductionmentioning

confidence: 99%

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Shapiro steps for skyrmion motion on a washboard potential with longitudinal and transverse ac drives

Reichhardt

2015

Phys. Rev. B

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We numerically study the behavior of two-dimensional skyrmions in the presence of a quasi-onedimensional sinusoidal substrate under the influence of externally applied dc and ac drives. In the overdamped limit, when both dc and ac drives are aligned in the longitudinal direction parallel to the direction of the substrate modulation, the velocity-force curves exhibit classic Shapiro step features when the frequency of the ac drive matches the washboard frequency that is dynamically generated by the motion of the skyrmions over the substrate, similar to previous observations in superconducting vortex systems. In the case of skyrmions, the additional contribution to the skyrmion motion from a non-dissipative Magnus force shifts the location of the locking steps to higher dc drives, and we find that the skyrmions move at an angle with respect to the direction of the dc drive. For a longitudinal dc drive and a perpendicular or transverse ac drive, the overdamped system exhibits no Shapiro steps; however, when a finite Magnus force is present we find pronounced transverse Shapiro steps along with complex two-dimensional periodic orbits of the skyrmions in the phaselocked regimes. Both the longitudinal and transverse ac drives produce locking steps whose widths oscillate with increasing ac drive amplitude. We examine the role of collective skyrmion interactions and find that additional fractional locking steps occur for both longitudinal and transverse ac drives. At higher skyrmion densities, the system undergoes a series of dynamical order-disorder transitions, with the skyrmions forming a moving solid on the phase locking steps and a fluctuating dynamical liquid in regimes between the steps.

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Section: Collective Effectsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Shapiro steps for skyrmion motion on a washboard potential with longitudinal and transverse ac drives

Reichhardt

2015

Phys. Rev. B

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“…A critical current I c is defined as a threshold current at which the vortices start to move, using a 10 −7 V criterion [8]. , is not observed for either geometry.…”

Section: Resultsmentioning

confidence: 99%

“…We prepared two a-Mo x Ge 1−x films (films 1 and 2) with thickness d =330 nm independently by rf sputtering on a Si substrate held at room temperature [7,8]. The mean-field transition temperature T c0 and the zero-resistivity (ρ = 0) temperature T c for both films are 6.3 and 6.2 K, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…We measure voltage noise spectra S V (f ) in various B including the peak-effect (PE) regime [2][3][4][5][6][7][8], where I c shows a peak with B. Judging from the PE behavior of I c (B) and mode-locking resonance, the equilibrium solid state is considered to be a weakly disordered vortex lattice [7,8]. Preliminary results related to present work have been published elsewhere [9].…”

Section: Introductionmentioning

confidence: 99%

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