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Skyrmions in chiral magnets

Skyrmions are nanoscale particlelike magnetic textures discovered in chiral magnets in 2009. Since that time the field has shown tremendous growth, with the identification of more and more skyrmion-supporting materials and the development of additional experimental techniques capable of directly accessing the skyrmion dynamics. Skyrmions represent an example of a collectively interacting system of particles that can exhibit depinning and sliding phenomena, but unlike other such systems, due to the skyrmion topology a Magnus term plays a strong role in the skyrmion dynamics. Numerous recent theoretical and experimental papers have demonstrated that this Magnus term strongly affects the skyrmion motion and the interactions of the skyrmions with quenched disorder or pinning. We explore the rich dynamics that emerge in this novel system.

Preprints:

  1. Asymmetric diffusion of chiral skyrmions
    X. Zhang, C. Reichhardt, C.J.O. Reichhardt, Y. Zhou, Y. Xu, and M. Mochizuki
    Brownian dynamics of chiral matter in chiral environment may give rise to emergent phenomena that could not be observed in achiral environment. Here, we report the asymmetric diffusion of chiral skyrmions in two chambers separated by a chiral gate. The topology-determined Brownian gyromotion of skyrmions could lead to effective interactions between skyrmions and chamber walls with a sense of clockwise or counter-clockwise rotation. By fabricating a chiral gate separating two chambers, skyrmions could demonstrate asymmetric diffusion through the gate to approach a nonequilibrium state before reaching the thermal equilibrium. We focus on the asymmetric diffusion of skyrmions that depends on the gate chirality and opening width. Although the simulated diffusion of skyrmions is affected by the skyrmion density, which varies with time due to the diffusion and annihilation, the simulated outcomes are generally in line with simple theories assuming time-independent diffusion rates. Our results uncover asymmetric diffusive behaviors of chiral skyrmions interacting with chiral nanostructures, which will appeal to the wide audience interested in hard condensed matter systems, magnetism, active matter, and statistical physics. arXiv
  2. Ordered and disordered skyrmion states on a square substrate
    J.C. Bellizotti Souza, C.J.O. Reichhardt, C. Reichhardt, N.P. Vizarim, and P.A. Venegas
    arXiv
    We examine the ordering of skyrmions interacting with a square substrate created from a modulation of anisotropy using atomistic simulations. We consider fillings of f = 1.5, 2.0, 2.5, 3.0, and 3.5 skyrmions per potential minimum as a function of magnetic field and sample size. For a filling of f = 2.0, we find various dimer orderings, such as tilted dimer states, as well as antiferromagnetic ordering that is similar to the colloidal dimer ordering seen on square substrates. The ability of the skyrmions to change shape or annihilate produces additional states that do not occur in the colloidal systems. For certain parameters at f = 2.0, half of the skyrmions can annihilate to form a square lattice, or a superlattice of trimers and monomers containing skyrmions of different sizes can form. At lower fields, ordered stretched skyrmion states can appear, and for zero field, there can be ordered stripe states. For f = 3.0, we find ferromagnetic ordered trimers, tilted lattices, columnar lattices, and stretched phases. For fillings of f = 1.5 and 2.5, we find bipartite lattices, different ordered and disordered states, and several extended disordered regions produced by frustration effects.


Papers:

  1. Sliding dynamics of skyrmion molecular crystals
    J.C. Bellizotti Souza, C.J.O. Reichhardt, C. Reichhardt, N.P. Vizarim, and P.A. Venegas
    J. Phys.: Condens. Matter, in press (2025) arXiv
  2. Skyrmion-skyrmionium phase separation and laning transitions via spin-orbit torque currents
    N.P. Vizarim, J.C. Bellizotti Souza, C.J.O. Reichhardt, C. Reichhardt, P.A. Venegas, and F. Beron
    Phys. Rev. B, in press (2025). arXiv


  3. Topological transitions, pinning and ratchets for driven magnetic hopfions in nanostructures
    J.C. Bellizotti Souza, C.J.O. Reichhardt, C. Reichhardt, A. Saxena, N.P. Vizarim, and P.A. Venegas
    Sci. Rep. 15, 16802 (2025). arXiv


  4. Skyrmionium dynamics and stability on one dimensional anisotropy patterns
    J.C. Bellizotti Souza, N.P. Vizarim, C.J.O. Reichhardt, C. Reichhardt, and P.A. Venegas
    J. Phys.: Condens. Matt. 37, 195802 (2025). arXiv


  5. Comparing dynamics, pinning and ratchet effects for skyrmionium, skyrmions, and antiskyrmions
    J.C. Bellizotti Souza, N.P. Vizarim, C.J.O. Reichhardt, C. Reichhardt, and P.A. Venegas
    J. Phys.: Condens. Matt. 37, 165801 (2025). arXiv


  6. Skyrmion soliton motion on periodic substrates by atomistic and particle based simulations
    J.C. Bellizotti Souza, N.P. Vizarim, C.J.O. Reichhardt, C. Reichhardt, and P.A. Venegas
    EPL 148, 56002 (2024). arXiv


  7. Reversible to irreversible transitions for ac driven skyrmions on periodic substrates
    J.C. Bellizotti Souza, N.P. Vizarim, C.J.O. Reichhardt, C. Reichhardt, and P.A. Venegas
    New J. Phys. 26, 113007 (2024). arXiv


  8. Skyrmion molecular crystals and superlattices on triangular substrates
    J.C. Bellizotti Souza, N.P. Vizarim, C.J.O. Reichhardt, P.A. Venegas, and C. Reichhardt
    Phys. Rev. B 111, 054402 (2025). arXiv


  9. Shapiro steps and stability of skyrmions interacting with alternating anisotropy under the influence of ac and dc drives
    J.C. Bellizotti Souza, N.P. Vizarim, C.J.O. Reichhardt, C. Reichhardt, and P.A. Venegas
    Phys. Rev. B 110, 014406 (2024). arXiv


  10. Controlled skyrmion ratchet in linear protrusion defects
    F.S. Rocha, J.C. Bellizotti Souza, N.P. Vizarim, C.J.O. Reichhardt, C. Reichhardt, and P.A. Venegas
    Phys. Rev. B 109, 054407 (2024). arXiv


  11. Skyrmion transport and annihilation in funnel geometries
    F.S. Rocha, J.C. Bellizotti Souza, N.P. Vizarim, C.J.O. Reichhardt, C. Reichhardt, and P.A. Venegas
    J. Phys.: Condens. Matter 36, 115801 (2024). arXiv


  12. Soliton motion induced along ferromagnetic skyrmion chains in chiral thin nanotracks
    J.C. Bellizotti Souza, N.P. Vizarim, C.J.O. Reichhardt, C. Reichhardt, and P.A. Venegas
    J. Mag. Mag. Mater. 587, 171280 (2023). arXiv


  13. Kibble-Zurek scenario and coarsening across nonequilibrium phase transitions in driven vortices and skyrmions
    C. Reichhardt and C.J.O. Reichhardt
    Phys. Rev. Res. 5, 033221 (2023). arXiv


  14. Peak effect, melting, and transport in skyrmion crystals
    C. Reichhardt and C.J.O. Reichhardt
    Phys. Rev. B 108, 014428 (2023). arXiv


  15. Spontaneous skyrmion conformal lattice and transverse motion during dc and ac compression
    J.C. Bellizotti Souza, N.P. Vizarim, C.J.O. Reichhardt, C. Reichhardt, and P.A. Venegas
    New J. Phys. 25, 053020 (2023). arXiv


  16. Magnus induced diode effect for skyrmions in channels with periodic potentials
    J.C. Bellizotti Souza, N.P. Vizarim, C.J.O. Reichhardt, C. Reichhardt, and P.A. Venegas
    J. Phys.: Condens. Matter 51, 015804 (2022). arXiv


  17. Editorial: Generation, detection and manipulation of skyrmions in magnetic nanostructures
    H.Y. Yuan, X. Zhang, and C.J.O. Reichhardt
    Front. Phys. 10, 964975 (2022).


  18. Dynamic phases and reentrant Hall effect for vortices and skyrmions on periodic pinning arrays
    C.J.O. Reichhardt and C. Reichhardt
    Eur. Phys. J. B 95, 135 (2022). arXiv


  19. Clogging, diode and collective effects of skyrmions in funnel geometries
    J.C. Bellizotti Souza, N.P. Vizarim, C.J.O. Reichhardt, C. Reichhardt, and P.A. Venegas
    New J. Phys. 24, 103030 (2022). arXiv


  20. Statics and dynamics of skyrmions interacting with disorder and nanostructures
    C. Reichhardt, C.J.O. Reichhardt, and M.V. Milosevic
    Rev. Mod. Phys. 94, 035005 (2022). arXiv


  21. Commensuration effects on skyrmion Hall angle and drag for manipulation of skyrmions on two-dimensional periodic substrates
    C. Reichhardt and C.J.O. Reichhardt
    Phys. Rev. B 105, 214437 (2022). arXiv


  22. Soliton motion in skyrmion chains: Stabilization and guidance by nanoengineered pinning
    N.P. Vizarim, J.C. Bellizotti Souza, C.J.O. Reichhardt, C. Reichhardt, M.V. Milosevic, and P.A. Venegas
    Phys. Rev. B 105, 224409 (2022). arXiv


  23. Directed motion of liquid crystal skyrmions with oscillating fields
    A. Duzgun, C. Nisoli, C.J.O. Reichhardt, and C. Reichhardt
    New J. Phys. 24, 033033 (2022). arXiv


  24. Fluctuations and pinning for individually manipulated skyrmions
    C.J.O. Reichhardt and C. Reichhardt
    Front. Phys. 9, 767491 (2021). arXiv


  25. Visualizing the strongly reshaped skyrmion Hall effect in multilayer wire devices
    A.K.C. Tan, P. Ho, J. Lourembam, L. Huang, H.K. Tan, C.J.O. Reichhardt, C. Reichhardt, and A. Soumyanarayan
    Nature Commun. 12, 4252 (2021). arXiv


  26. Dynamics and nonmonotonic drag for individually driven skyrmions
    C. Reichhardt and C.J.O. Reichhardt
    Phys. Rev. B 104, 064441 (2021). arXiv


  27. Skyrmion ratchet in funnel geometries
    J.C. Bellizotti Souza, N.P. Vizarim, C.J.O. Reichhardt, C. Reichhardt, and P.A. Venegas
    Phys. Rev. B 104, 054434 (2021). arXiv


  28. Directional locking and the influence of obstacle density on skyrmion dynamics in triangular and honeycomb arrays
    N.P. Vizarim, J.C. Bellizotti Souza, C. Reichhardt, C.J.O. Reichhardt, and P.A. Venegas
    J. Phys.: Condens. Matter 33, 305801 (2021). arXiv


  29. Guided skyrmion motion along pinning array interfaces
    N.P. Vizarim, C. Reichhardt, P.A. Venegas, and C.J.O. Reichhardt
    J. Mag. Mag. Mater. 528, 167710 (2021). arXiv


  30. Skyrmion pinball and directed motion on obstacle arrays
    N.P. Vizarim, C.J.O. Reichhardt, P.A. Venegas, and C. Reichhardt
    J. Phys. Commun. 4, 085001 (2020). arXiv


  31. Shapiro steps and nonlinear skyrmion Hall angles for dc and ac driven skyrmions on a two dimensional periodic substrate
    N.P. Vizarim, C. Reichhardt, P.A. Venegas, and C.J.O. Reichhardt
    Phys. Rev. B 102, 104413 (2020). arXiv


  32. Skyrmion dynamics and transverse mobility: Skyrmion Hall angle reversal on 2D periodic substrates with dc and biharmonic ac drives
    N.P. Vizarim, C.J.O. Reichhardt, P.A. Venegas, and C. Reichhardt
    Eur. Phys. J. B 93, 112 (2020) arXiv


  33. Dynamics of Magnus dominated particle clusters, collisions, pinning and ratchets
    C. Reichhardt and C.J.O. Reichhardt
    Phys. Rev. E 101, 062602 (2020). arXiv


  34. Skyrmion dynamics and topological sorting on periodic obstacle arrays
    N.P. Vizarim, C. Reichhardt, C.J.O. Reichhardt, and P.A. Venegas
    New J. Phys. 22, 053025 (2020). arXiv


  35. Commensurate states and pattern switching via liquid crystal skyrmions trapped in a square lattice
    A. Duzgun, C. Nisoli, C.J.O. Reichhardt, and C. Reichhardt
    Soft Matter 16, 3338 (2020). arXiv


  36. Shear banding, intermittency, jamming and dynamic phases for skyrmions in inhomogeneous pinning arrays
    C. Reichhardt and C.J.O. Reichhardt
    Phys. Rev. B 101, 054423 (2020). arXiv


  37. Chiral edge currents for ac driven skyrmions in confined pinning geometries
    C. Reichhardt and C.J.O. Reichhardt
    Phys. Rev. B 100, 174414 (2019). arXiv


  38. Reentrant pinning, dynamic row reduction, and skyrmion accumulation for driven skyrmions in inhomogeneous pinning arrays
    C. Reichhardt and C.J.O. Reichhardt
    EPL 129, 21001 (2020). arXiv


  39. Nonlinear transport, dynamic ordering, and clustering for driven skyrmions on random pinning
    C. Reichhardt and C.J.O. Reichhardt
    Phys. Rev. B 99, 104418 (2019). arXiv


  40. Skyrmions in anisotropic magnetic fields: Strain and defect dynamics
    R. Brearton, M.W. Olszewski, S. Zhang, M.R. Eskildsen, C. Reichhardt, C.J.O. Reichhardt, G. van der Laan, and T. Hesjedal
    MRS Adv. 4, 643 (2019).


  41. Disordering, clustering, and laning transitions in particle systems with dispersion in the Magnus term
    C.J.O. Reichhardt and C. Reichhardt
    Phys. Rev. E 99, 012606 (2019). arXiv


  42. Reversible to irreversible transitions in periodically driven skyrmion systems
    B.L. Brown, C. Reichhardt, and C.J.O. Reichhardt
    New J. Phys. 21, 013001 (2019). arXiv


  43. Thermal creep and the skyrmion Hall angle in driven skyrmion crystals
    C. Reichhardt and C.J.O. Reichhardt
    J. Phys.: Condens. Matter 31, 07LT01 (2019). arXiv


  44. Nonequilibrium phases and segregation for skyrmions on periodic pinning arrays
    C. Reichhardt, D. Ray, and C.J.O. Reichhardt
    Phys. Rev. B 98, 134418 (2018). arXiv


  45. Avalanches and criticality in driven magnetic skyrmions
    S.A. Diaz, C. Reichhardt, D.P. Arovas, A. Saxena, and C.J.O. Reichhardt
    Phys. Rev. Lett. 120, 117203 (2018). arXiv


  46. Fluctuations and noise signatures of driven magnetic skyrmions
    S.A. Diaz, C.J.O. Reichhardt, D.P. Arovas, A. Saxena, and C. Reichhardt
    Phys. Rev. B 96, 085106 (2017). arXiv


  47. Reversible vector ratchets for skyrmion systems
     X. Ma, C.J. Olson Reichhardt, and C. Reichhardt
    Phys. Rev. B 95, 104401 (2017). arXiv


  48. Shapiro spikes and negative mobility for skyrmion motion on quasi-one-dimensional periodic substrates
    C. Reichhardt and C.J. Olson Reichhardt
    Phys. Rev. B 95, 014412 (2017). arXiv


  49. Noise fluctuations and drive dependence of the skyrmion Hall effect in disordered systems
     C. Reichhardt and C.J. Olson Reichhardt
    New J. Phys. 18, 095005 (2016). arXiv


  50. Emergent geometric frustration of artificial magnetic skyrmion crystals
     F. Ma, C. Reichhardt, W. Gan, C.J. Olson Reichhardt, and W.S. Lew
    Phys. Rev. B 94, 144405 (2016) arXiv


  51. Magnus-induced dynamics of driven skyrmions on a quasi-one-dimensional periodic substrate
     C. Reichhardt and C.J. Olson Reichhardt
    Phys. Rev. B 94, 094413 (2016). arXiv


  52. Shapiro steps for skyrmion motion on a washboard potential with longitudinal and transverse ac drives
     C. Reichhardt and C.J. Olson Reichhardt
    Phys. Rev. B 92, 224432 (2015). arXiv


  53. Magnus-induced ratchet effects for skyrmions interacting with asymmetric substrates
    C. Reichhardt, D. Ray, and C.J. Olson Reichhardt
    New J. Phys. 17, 073034 (2015). arXiv


  54. Quantized transport for a skyrmion moving on a two-dimensional periodic substrate
    C. Reichhardt, D. Ray, and C.J. Olson Reichhardt
    Phys. Rev. B 91, 104426 (2015). arXiv


  55. Collective transport properties of driven skyrmions with random disorder
    C. Reichhardt, D. Ray, and C.J. Olson Reichhardt
    Phys. Rev. Lett. 114, 217202 (2015). arXiv


  56. Comparing the dynamics of skyrmions and superconducting vortices
    C.J. Olson Reichhardt, S.Z. Lin, D. Ray, and C. Reichhardt
    Physica C 503, 52 (2014). arXiv

Last modified Jan 7, 2019