Two-Fluid Theory for Spin Superfluidity in Magnetic Insulators

Flebus, B.; Bender, S. A.; Tserkovnyak, Y.; Duine, R. A.

doi:10.48550/arxiv.1510.05316

Cited by 3 publications

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“…where V el kk is the matrix element for scattering by defects and rough boundaries [23,37] of a magnon with momentum k to one with k at the same energy. Γ in el is obtained from this expression by interchanging k and k .…”

Section: Discussionmentioning

confidence: 99%

“…These are defined from the "out" rates via J s ω/ or τ el = el /v m , where v m = 2 J s ω/ is the magnon group velocity. Estimates for el range from 1 µm [23] under the assumption that m is due to Gilbert damping and disorder only, to 500 µm [37]. Therefore τ el ∼ 10 − 10 5 ps.…”

Section: Discussionmentioning

confidence: 99%

“…We first review the diffusion theory for electrical magnon spin injection and detection as published by one of us in [17,23]. By introducing the magnon chemical potential this approach can disentangle spin and heat transport in contrast to earlier treatments based on the magnon density [20] or magnon temperature [1,[5][6][7] only.…”

Section: Theorymentioning

confidence: 99%

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Magnon spin transport driven by the magnon chemical potential in a magnetic insulator

et al. 2016

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We develop a linear-response transport theory of diffusive spin and heat transport by magnons in magnetic insulators with metallic contacts. The magnons are described by a position dependent temperature and chemical potential that are governed by diffusion equations with characteristic relaxation lengths. Proceeding from a linearized Boltzmann equation, we derive expressions for length scales and transport coefficients. For yttrium iron garnet (YIG) at room temperature we find that long-range transport is dominated by the magnon chemical potential. We compare the model's results with recent experiments on YIG with Pt contacts [L. J. Cornelissen, et al., Nat. Phys. 11, 1022] and extract a magnon spin conductivity of σm = 5 × 10 5 S/m. Our results for the spin Seebeck coefficient in YIG agree with published experiments. We conclude that the magnon chemical potential is an essential ingredient for energy and spin transport in magnetic insulators.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Magnon spin transport driven by the magnon chemical potential in a magnetic insulator

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“…Two-fluid magnon hydrodynamics.-The interplay between thermal-magnon transport and coherent orderparameter dynamics is naturally captured within the arXiv:1512.00557v1 [cond-mat.mes-hall] 2 Dec 2015 two-fluid formalism developed in Ref. [21]. Namely, we start with a generic long-wavelength spin Hamiltonian…”

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confidence: 99%

“…Following the Landau-Lifshitz-Gilbert (LLG) phenomenology [23] of long-wavelength spin-wave dynamics, the following hydrodynamic equations are obtained [21]:…”

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Bose-Einstein condensation of magnons pumped by the bulk spin Seebeck effect

et al. 2016

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We propose inducing Bose-Einstein condensation of magnons in a magnetic insulator by a heat flow oriented toward its boundary. At a critical heat flux, the oversaturated thermal gas of magnons accumulated at the boundary precipitates the condensate, which then grows gradually as the thermal bias is dialed up further. The thermal magnons thus pumped by the magnonic bulk (spin) Seebeck effect must generally overcome both the local Gilbert damping associated with the coherent magnetic dynamics as well as the radiative spin-wave losses toward the magnetic bulk, in order to achieve the threshold of condensation. We quantitatively estimate the requisite bias in the case of the ferrimagnetic yttrium iron garnet, discuss different physical regimes of condensation, and contrast it with the competing (so-called Doppler-shift) bulk instability.

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Magnons and Phonons Optically Driven out of Local Equilibrium in a Magnetic Insulator

Olsson

Weathers

et al. 2016

Phys. Rev. Lett.

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The coupling and possible nonequilibrium between magnons and other energy carriers have been used to explain several recently discovered thermally driven spin transport and energy conversion phenomena. Here, we report experiments in which local nonequilibrium between magnons and phonons in a single crystalline bulk magnetic insulator, Y_{3}Fe_{5}O_{12}, has been created optically within a focused laser spot and probed directly via micro-Brillouin light scattering. Through analyzing the deviation in the magnon number density from the local equilibrium value, we obtain the diffusion length of thermal magnons. By explicitly establishing and observing local nonequilibrium between magnons and phonons, our studies represent an important step toward a quantitative understanding of various spin-heat coupling phenomena.

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Two-Fluid Theory for Spin Superfluidity in Magnetic Insulators

Cited by 3 publications

References 0 publications

Magnon spin transport driven by the magnon chemical potential in a magnetic insulator

Magnon spin transport driven by the magnon chemical potential in a magnetic insulator

Bose-Einstein condensation of magnons pumped by the bulk spin Seebeck effect

Magnons and Phonons Optically Driven out of Local Equilibrium in a Magnetic Insulator

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