Dirac electrons and domain walls: A realization in junctions of ferromagnets and topological insulators

Ferreirós, Yago; Buijnsters, F. J.; Katsnelson, M. I.

doi:10.1103/physrevb.92.085416

Cited by 21 publications

(21 citation statements)

References 77 publications

(136 reference statements)

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“…In chiral spin textures hosting mixed Weyl semimetallic states, we anticipate that such electronic puddles will result in topologically distinct contributions to the current-driven spin torques acting on these spin structures, a prominent variation of the texture-induced Hall signal in real space, chiral and topological orbital magnetism [68][69][70] , as well as "topological" contributions to the longitudinal transport properties of domain walls and chiral magnetic skyrmions made of mixed Weyl semimetals. Interfaces between topological insulators and dynamic magnetization structures present further compelling examples of such complex mixed topologies [71][72][73] . We thereby proclaim that exploring the avenues associated with the exotic electronic, transport, and response phenomena in textured mixed semimetals presents one of the most exciting challenges in topological chiral spintronics.…”

Section: Resultsmentioning

confidence: 99%

Mixed topological semimetals driven by orbital complexity in two-dimensional ferromagnets

et al. 2019

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The concepts of Weyl fermions and topological semimetals emerging in three-dimensional momentum space are extensively explored owing to the vast variety of exotic properties that they give rise to. On the other hand, very little is known about semimetallic states emerging in two-dimensional magnetic materials, which present the foundation for both present and future information technology. Here, we demonstrate that including the magnetization direction into the topological analysis allows for a natural classification of topological semimetallic states that manifest in two-dimensional ferromagnets as a result of the interplay between spin-orbit and exchange interactions. We explore the emergence and stability of such mixed topological semimetals in realistic materials, and point out the perspectives of mixed topological states for current-induced orbital magnetism and current-induced domain wall motion. Our findings pave the way to understanding, engineering and utilizing topological semimetallic states in two-dimensional spin-orbit ferromagnets.

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Section: Resultsmentioning

confidence: 99%

Mixed topological semimetals driven by orbital complexity in two-dimensional ferromagnets

et al. 2019

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“…Secondly, the surface Hall currents and chiral modes exert exchange coupling-induced spin torque on the magnetic order both in and out of equilibrium. Here, the magnetoelectric effects explored theoretically include: surface Hall currents-induced switching of monodomain magnets [7]; coupled dynamics of domain wall and chiral mode imprinted by the wall [8] [9]; and equilibrium spin torqueinduced interfacial anisotropy and Dzyaloshinskii-Moriya interaction [10].…”

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confidence: 99%

Domain wall in a quantum anomalous Hall insulator as a magnetoelectric piston

Upadhyaya

Tserkovnyak

2016

Phys. Rev. B

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We theoretically study the magnetoelectric coupling in a quantum anomalous Hall insulator state induced by interfacing a dynamic magnetization texture to a topological insulator. In particular, we propose that the quantum anomalous Hall insulator with a magnetic configuration of a domain wall, when contacted by electrical reservoirs, acts as a magnetoelectric piston. A moving domain wall pumps charge current between electrical leads in a closed circuit, while applying an electrical bias induces reciprocal domain-wall motion. This piston-like action is enabled by a finite reflection of charge carriers via chiral modes imprinted by the domain wall. Moreover, we find that, when compared with the recently discovered spin-orbit torque-induced domain-wall motion in heavy metals, the reflection coefficient plays the role of an effective spin-Hall angle governing the efficiency of the proposed electrical control of domain walls. Quantitatively, this effective spin-Hall angle is found to approach a universal value of 2, providing an efficient scheme to reconfigure the domain-wall chiral interconnects for possible memory and logic applications.PACS numbers: 72.15.Gd, Introduction. Motivated by the possibility of realizing unique magnetoelectric phenomena, breaking of timereversal symmetry in recently discovered topological insulators (TIs) 1 has become one of the central themes of theoretical and experimental research. In particular, a proximal magnetic order can induce a gap in an otherwise linear spectrum of the Dirac electrons residing on the surface of a TI, resulting in a phase transition to a quantum anomalous Hall (QAH) state 2 . This QAH phase manifests itself via the appearance of quantized surface Hall currents and chiral modes (at the boundary where the gap vanishes), which, in turn, give rise to two types of magnetoelectric effects. Firstly, the Oersted fields originating from the surface Hall currents result in a topological magnetoelectric effect 3 (a condensed matter realization of axion electrodynamics 4 ). Examples of predicted consequences of this magnetoelectric effect include: appearance of image magnetic monopole 5 and charging of magnetization textures 6 . Secondly, the surface Hall currents and chiral modes exert exchange coupling-induced spin torque on the magnetic order both in and out of equilibrium. Here, the magnetoelectric effects explored theoretically include: surface Hall currents-induced switching of monodomain magnets 7 ; coupled dynamics of domain wall and chiral mode imprinted by the wall 89 ; and equilibrium spin torque-induced interfacial anisotropy and Dzyaloshinskii-Moriya interaction 10 .Technologically, the magnetoelectric effects in QAH regime provide an opportunity to construct spintronic devices with minimal dissipation 7 , thanks to the dissipationless nature of Hall currents and chiral propagation. A prototypical example of a spintronic application envisioned for next generation information processing is based on a domain-wall, owing to its nonvolatile nature. In such a devi...

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“…Different routes include the use of magnetoelectric coupling [3] or spin-polarized currents [4][5][6]. More recently, new possibilities have appeared with the advent of metallic topological states of matter, which started with studies on electric control of magnetization by the surface states of topological insulators [7][8][9][10][11][12][13][14][15], and continued with works on spin-to-charge conversion [16] and spin torques [17,18] in magnetic Weyl semimetals. Both systems share a strong spin-momentum locking.…”

Section: Introductionmentioning

confidence: 99%

Electric manipulation of domain walls in magnetic Weyl semimetals via the axial anomaly

et al. 2021

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We show how the axial (chiral) anomaly induces a spin torque on the magnetization in magnetic Weyl semimetals. The anomaly produces an imbalance in left- and right-handed chirality carriers when non-orthogonal electric and magnetic fields are applied. Such imbalance generates a spin density which exerts a torque on the magnetization, the strength of which can be controlled by the intensity of the applied electric field. We show how this results in an electric control of the chirality of domain walls, as well as in an improvement of the domain wall dynamics, by delaying the onset of the Walker breakdown. The measurement of the electric field mediated changes in the domain wall chirality would constitute a direct proof of the axial anomaly. Additionally, we show how quantum fluctuations of electronic Fermi arc states bound to the domain wall naturally induce an effective magnetic anisotropy, allowing for high domain wall velocities even if the intrinsic anisotropy of the magnetic Weyl semimetal is small.

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Dirac electrons and domain walls: A realization in junctions of ferromagnets and topological insulators

Cited by 21 publications

References 77 publications

Mixed topological semimetals driven by orbital complexity in two-dimensional ferromagnets

Mixed topological semimetals driven by orbital complexity in two-dimensional ferromagnets

Domain wall in a quantum anomalous Hall insulator as a magnetoelectric piston

Electric manipulation of domain walls in magnetic Weyl semimetals via the axial anomaly

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