Comparing the dynamics of skyrmions and superconducting vortices

Lin, Shi-Zeng; Ray, Dipanjan; Reichhardt, C.

doi:10.1016/j.physc.2014.03.029

Cited by 14 publications

(9 citation statements)

References 60 publications

(75 reference statements)

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“…Up until now, however, analogous studies of skyrmion lattices have not been reported even though (as for superconducting vortices) it is well-known that defects and dislocations present in a sample can pin the motion of skyrmions induced by external perturbations such as an electric field [19] or a magnetic field [15]. This competition between disorder and elasticity will clearly give rise to a complex energy landscape promoting diverse metastable states [20], and superstructures [21,22]. Furthermore, up to now, previous imaging studies of skyrmion lattices could probe only the short range order due to limitations in the size of the imaged area and its homogeneity.…”

Section: Introductionmentioning

confidence: 99%

Filming the formation and fluctuation of skyrmion domains by cryo-Lorentz transmission electron microscopy

Rajeswari

Huang

Mancini

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Magnetic skyrmions are promising candidates as information carriers in logic or storage devices thanks to their robustness, guaranteed by the topological protection, and their nanometric size. Currently, little is known about the influence of parameters such as disorder, defects, or external stimuli on the long-range spatial distribution and temporal evolution of the skyrmion lattice. Here, using a large (7.3 × 7.3 μm 2 ) single-crystal nanoslice (150 nm thick) of Cu 2 OSeO 3 , we image up to 70,000 skyrmions by means of cryo-Lorentz transmission electron microscopy as a function of the applied magnetic field. The emergence of the skyrmion lattice from the helimagnetic phase is monitored, revealing the existence of a glassy skyrmion phase at the phase transition field, where patches of an octagonally distorted skyrmion lattice are also discovered. In the skyrmion phase, dislocations are shown to cause the emergence and switching between domains with different lattice orientations, and the temporal fluctuation of these domains is filmed. These results demonstrate the importance of direct-space and real-time imaging of skyrmion domains for addressing both their long-range topology and stability.skyrmions | Lorentz transmission electron microscopy | skyrmion dynamics | magnetic materials | strongly correlated systems I n a noncentrosymmetric chiral lattice, the competition between the symmetric ferromagnetic exchange, the antisymmetric Dzyaloshinskii-Moriya interaction, and an applied magnetic field can stabilize a highly ordered spin texture, presenting as a hexagonal lattice of spin vortices called skyrmions (1-4).Magnetic skyrmions have been experimentally detected in materials having the B20 crystal structure such as MnSi (5), Fe 1−x Co x Si (6, 7), FeGe (8), and Cu 2 OSeO 3 (9) and, recently, also on systems like GaV 4 S 8 (10) and beta-Mn-type alloys (11). Small-angle neutron scattering studies of bulk solids evidenced the formation of a hexagonal skyrmion lattice confined in a very narrow region of temperature and magnetic field (T-B) in the phase diagram (5, 6). In thin films and thinly cut slices of the same compounds, instead, skyrmions can be stabilized over a wider T-B range as revealed by experiments using cryo-Lorentz transmission electron microscopy (LTEM) (12, 13). Furthermore, it was proposed and recently observed that skyrmions can also exist as isolated objects before the formation of the ordered skyrmion lattice (14, 15). A recent resonant X-ray diffraction experiment also suggested the formation of two skyrmion sublattices giving rise to regular superstructures (16).In a 2D landscape, long-range ordering can be significantly altered by the presence of defects and disorder. Indeed, the competition between order and disorder within the context of lattice formation continues to be an issue of fundamental importance.Condensed matter systems are well known to provide important test beds for exploring theories of structural order in solids and glasses. An archetypal and conceptually relevant example ...

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Section: Introductionmentioning

confidence: 99%

Filming the formation and fluctuation of skyrmion domains by cryo-Lorentz transmission electron microscopy

Rajeswari

Huang

Mancini

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…Using Thiele's approach [14,15], which treats skyrmions as rigid pointlike particles, equations of motion can be derived [10] that lend themselves to in-depth numerical simulations of interacting skyrmion systems. A similar treatment has been used to derive equations of motion for vortices in type-II superconductors [16,17], and the resulting equations are in fact quite similar to those for skyrmions [18], except for the Magnus force which is usually negligible in vortex dynamics. The Magnus force acts normal to the drift velocity of the skyrmion and can therefore cause orbits or spiraling trajectories.…”

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confidence: 99%

Effect of the Magnus force on skyrmion relaxation dynamics

2018

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We perform systematic Langevin molecular dynamics simulations of interacting skyrmions in thin films. The interplay between Magnus force, repulsive skyrmion-skyrmion interaction and thermal noise yields different regimes during non-equilibrium relaxation. In the noise-dominated regime the Magnus force enhances the disordering effects of the thermal noise. In the Magnus-force-dominated regime, the Magnus force cooperates with the skyrmion-skyrmion interaction to yield a dynamic regime with slow decaying correlations. These two regimes are characterized by different values of the aging exponent. In general, the Magnus force accelerates the approach to the steady state.

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“…For example, such studies would help evaluate whether the vortex lattice may undergo a structural transition. These results may also shed light on understanding plasticity in other systems, including materials containing skyrmions [79][80][81], domain walls [82,83], and charge density waves [84,85].…”

Section: B Plastic Deformations Of the Vortex Latticementioning

confidence: 79%

Plastic vortex creep and dimensional crossovers in the highly anisotropic superconductor HgBa$_2$CuO$_{4+x}$

M.¹,

Venuti²,

Gorman³

et al. 2021

Preprint

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In type-II superconductors exposed to magnetic fields between upper and lower critical values, Hc1 and Hc2, penetrating magnetic flux forms a lattice of vortices whose motion can induce dissipation. Consequently, the magnetization M of superconductors is typically progressively weakened with increasing magnetic field B ∝ nv (for vortex density nv). However, some materials exhibit a nonmonotonic M (B), presenting a maximum in M at what is known as the second magnetization peak. This phenomenon appears in most classes of superconductors, including low Tc materials, iron-based, and cuprates, complicating pinpointing its origin and garnering intense interest. Here, we report on vortex dynamics in optimally doped and overdoped HgBa2CuO4+x crystals, with a focus on a regime in which plastic deformations of the vortex lattice govern magnetic properties. Specifically, we find that both crystals exhibit conspicuous second magnetization peaks and, from measurements of the field-and temperature-dependent vortex creep rates, identify and characterize phase boundaries between elastic and plastic vortex dynamics, as well as multiple previously unreported transitions within the plastic flow regime. We find that the second magnetization peak coincides with the elastic-to-plastic crossover for a very small range of high fields, and a sharp crossover within the plastic flow regime for a wider range of lower fields. We find evidence that this transition in the plastic flow regime is due to a dimensional crossover, specifically a transition from 3D to 2D plastic dynamics.

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Comparing the dynamics of skyrmions and superconducting vortices

Cited by 14 publications

References 60 publications

Filming the formation and fluctuation of skyrmion domains by cryo-Lorentz transmission electron microscopy

Filming the formation and fluctuation of skyrmion domains by cryo-Lorentz transmission electron microscopy

Effect of the Magnus force on skyrmion relaxation dynamics

Plastic vortex creep and dimensional crossovers in the highly anisotropic superconductor HgBa$_2$CuO$_{4+x}$

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