Topological Transport of Deconfined Hedgehogs in Magnets

Zou, Ji; Zhang, Shu; Tserkovnyak, Yaroslav

doi:10.1103/physrevlett.125.267201

Cited by 22 publications

(13 citation statements)

References 73 publications

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“…No attempt has been made to classify scenarios of topological hydrodynamics for general quantum magnets in arbitrary dimensions, which also goes beyond our scope here. Quantum skyrmions in two spatial dimensions 27 and hedgehogs in three dimensions 28 provide other interesting examples, with skyrmions, like winding, obeying only an approximate continuity equation. We thus anticipate rich possibilities for topological hydrodynamics in magnetic materials, with implications for novel probes and device concepts that do not rely on electronic (charge) transport.…”

Section: Discussionmentioning

confidence: 99%

Quantum hydrodynamics of spin winding

Tserkovnyak,

Zou,

Kim

et al. 2020

Preprint

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An easy-plane spin winding in a quantum spin chain can be treated as a transport quantity, which propagates along the chain but has a finite lifetime due to phase slips. In a hydrodynamic formulation for the winding dynamics, the quantum continuity equation acquires a source term due to the transverse vorticity flow. The latter reflects the phase slips and generally compromises the global conservation law. A linear-response formalism for the nonlocal winding transport then reduces to a Kubo response for the winding flow along the spin chain, in conjunction with the parasitic vorticity flow transverse to it. One-dimensional topological hydrodynamics can be recovered when the vorticity flow is asymptotically small. Starting with a microscopic spin-chain formulation, we focus on the asymptotic behavior of the winding transport based on the renormalized sine-Gordon equation, incorporating phase slips as well as Gilbert damping. A generic electrical device is proposed to manifest this physics. We thus suggest winding conductivity as a tangible concept that can characterize low-energy dynamics in a broad class of quantum magnets. II. 2D VORTICITY (HYDRO)DYNAMICS A. Classical vorticity dynamicsA three-component real vector field m = (m x , m y , m z ) residing in 2+1 dimensions, m(r, t), realizes an R 2 → R 3 mapping, at any given time t. These spatial field textures are devoid of point defects, as the fundamental homo-

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Section: Discussionmentioning

confidence: 99%

Quantum hydrodynamics of spin winding

Tserkovnyak,

Zou,

Kim

et al. 2020

Preprint

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“…In the bottom of figure 1, we display three examples of such hedgehog crystals (HXs) composed of three proper-screw, cycloidal, and sinusoidal waves. Reflecting the noncollinear and noncoplanar spin configurations, all these spin textures exhibit unusual multiferroic phenomena and quantum transports through the spin Berry phase mechanism [31,32,33,34,35,36,37,38]. In this review, we call such multiple-Q magnetic states with nontrivial topology as "topological spin crystals" [39] * .…”

Section: Introductionmentioning

confidence: 99%

“…The spin and scalar chirality are shown in figures 12(a) and 12(b), respectively [23]. The scalar chirality at Q ν components on the triangular lattice is defined in a similar manner to (38) with the summation over the local scalar chirality χ sc R = S j • (S k × S l ), where R is the position vector at the center of triangle and j, k, l are three sites on the triangle in the counterclockwise order. * The state with interchanging Q 1 and Q 2 is energetically degenerate as expected from the symmetry.…”

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confidence: 99%

Topological spin crystals by itinerant frustration

Hayami,

Motome

2021

Preprint

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Spin textures with nontrivial topology, such as vortices and skyrmions, have attracted attention as a source of unconventional magnetic, transport, and optical phenomena. Recently, a new generation of topological spin textures has been extensively studied in itinerant magnets; in contrast to the conventional ones induced, e.g., by the Dzyaloshinskii-Moriya interaction in noncentrosymmetric systems, they are characterized by extremely short magnetic periods and stable even in centrosymmetric systems. Here we review such new types of topological spin textures with particular emphasis on their stabilization mechanism. Focusing on the interplay between charge and spin degrees of freedom in itinerant electron systems, we show that itinerant frustration, which is the competition among electron-mediated interactions, plays a central role in stabilizing a variety of topological spin crystals including a skyrmion crystal with unconventional high skyrmion number, meron crystals, and hedgehog crystals. We also show that the essential ingredients in the itinerant frustration are represented by bilinear and biquadratic spin interactions in momentum space. This perspective not only provides a unified understanding of the unconventional topological spin crystals but also stimulates further exploration of exotic topological phenomena in itinerant magnets.

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“…Now a large set of parameters in quantum estimation can be used to estimate the full quantum state of a system. This estimation of quantum state of the system by large set of parameters is done using quantum state tomography [49,50]. Thus, quantum state tomography has been used to obtain quantum states of various different quantum system [45,46,51].…”

Section: Introductionmentioning

confidence: 99%

Construction of Quantum Target Space from World-Sheet States using Quantum State Tomography

Wani,

Shabir,

Hassan

et al. 2021

Preprint

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In this paper, we will construct the quantum states of target space coordinates from world-sheet states, using quantum state tomography. To perform quantum state tomography of an open string, we will construct suitable quadrature operators. We do this by first defining the quadrature operators in world-sheet, and then using them to construct the quantum target space quadrature operators for an open string. We will connect the quantum target space to classical geometry using coherent string states. We will be using a novel construction based on a string displacement operator to construct these coherent states. The coherent states of the world-sheet will also be used to construct the coherent states in target space.

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Topological Transport of Deconfined Hedgehogs in Magnets

Cited by 22 publications

References 73 publications

Quantum hydrodynamics of spin winding

Quantum hydrodynamics of spin winding

Topological spin crystals by itinerant frustration

Construction of Quantum Target Space from World-Sheet States using Quantum State Tomography

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