Phase Locking of a Pair of Ferromagnetic Nano-oscillators on a Topological Insulator

Wang, Chengzhen; Xu, Hongya; Rizzo, Nicholas D.; Kiehl, R.A.; Lai, Ying–Cheng

doi:10.1103/physrevapplied.10.064003

Cited by 6 publications

(2 citation statements)

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“…For example, complicated dynamics can emerge in the magnetization switching due to a Hall-current-induced effective anisotropic field [18,[25][26][27] and steady self-oscillations can arise in an FMI/TI heterostructure [28][29][30]. A quite recent computational study has revealed phase locking in the magnetization dynamics of two FMIs on the top of a 3D TI [31].…”

Section: Introductionmentioning

confidence: 99%

Scattering of Dirac electrons from a skyrmion: Emergence of robust skew scattering

Wang

Lai

2020

Phys. Rev. Research

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We study electron scattering from a closed magnetic structure embedded in the top surface of a topological insulator (TI). Outside of the structure there is a uniform layer of ferromagnetic insulator (FMI), leading to a positive effective mass for the Dirac electrons. The mass inside the structure can be engineered to be negative, leading to a skyrmion structure. The geometric shape of the structure can be circular or deformed, leading to integrable or chaotic dynamics, respectively, in the classical limit. For a circular structure, the relativistic quantum scattering characteristics can be calculated analytically. For a deformed structure, we develop an efficient numerical method, the multiple multipole method, to solve the scattering wavefunctions. We find that, for scattering from a skyrmion, anomalous Hall effect as characterized by strong skew scattering can arise, which is robust against structural deformation due to the emergence of resonant modes. In the short (long) wavelength regime, the resonant modes manifest themselves as confined vortices (excited edge states). The origin of the resonant states is the spin phase factor of massive Dirac electrons at the skyrmion boundary. Further, in the short wavelength regime, for a circular skyrmion, a large number of angular momentum channels contribute to the resonant modes. In this regime, in principle, classical dynamics are relevant, but we find that geometric deformations, even those as severe as leading to fully developed chaos, have little effect on the resonant modes. The vortex structure of the resonant states makes it possible to electrically "charge" the skyrmion, rendering feasible to manipulate its motion electrically. In the long wavelength regime, only the lowest angular momentum channels contribute to the resonant modes, making the skew scattering sharply directional. These phenomena can be exploited for applications in generating dynamic skyrmions for information storage and in Hall devices.

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Section: Introductionmentioning

confidence: 99%

Scattering of Dirac electrons from a skyrmion: Emergence of robust skew scattering

Wang

Lai

2020

Phys. Rev. Research

Self Cite

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“…These states have been observed in other systems like 2D periodic lattice of Kuramoto oscillators 20 or ring structure of identical Kuramoto oscillators 21 . Previous simulation studies on two STNOs 22 , coupled through dipolar inter-action, have shown that depending on the initial condition or STNO configuration, it is possible to stabilize an in-phase or anti-phase synchronised state [23][24][25][26] . Such modes can be associated with different applications, for instance, the in-phase mode is required to enhance the emission power, and the anti-phase mode can be useful for applications in phased array radar systems or bio-inspired computing 27,28 .…”

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confidence: 99%