Spatially non-uniform ground state and quantized vortices in a two-component Bose-Einstein condensate of magnons

Nowik-Boltyk, P.; Dzyapko, O.; Demidov, V. E.; Berloff, Natalia G.; Demokritov, S. O.

doi:10.1038/srep00482

Cited by 90 publications

(97 citation statements)

References 34 publications

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“…Such a phase separation can lead to the formation of "domains" of magnons with different density of magnons having opposite wave numbers, and, as a consequence, to the reduction of the per-particle energy. A strong phase separation of magnons in mBEC is not observed in our experiments with spatial resolution [33,34] , and the pronounced domains cannot be formed under a relatively low pumping rate used in our experiments.…”

Section: Discussionmentioning

confidence: 70%

Magnon-magnon interactions in a room-temperature magnonic Bose-Einstein condensate

et al. 2017

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AbstactBose-Einstein condensate of magnons (mBEC) that is formed at room temperature in parametrically pumped magnetic films is double-degenerate: it is formed simultaneously in two spectral minima corresponding to the lowest energy magnons propagating in opposite directions along the in-plane bias magnetic field. In this work the interactions of magnons in the mBEC are studied both theoretically and experimentally. It is shown by direct calculation that the magnons residing in each of the degenerate spectral minima of mBEC form a practically ideal magnon gas, as the attractive self-interaction between these magnons is very weak. At the same time, the interaction between the magnons residing in different spectral minima, corresponding to the opposite directions of the magnon wave vector, is relatively strong and repulsive, leading to a repulsive total inter-magnon interaction. By measuring the spectral characteristics of the mBEC it is shown, that with the increased magnon density the energy per magnon in the mBECs increases, thus confirming experimentally that the net inter-magnon interaction in a doubledegenerate mBEC is repulsive.

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Section: Discussionmentioning

confidence: 70%

Magnon-magnon interactions in a room-temperature magnonic Bose-Einstein condensate

et al. 2017

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“…Kalinikos and Slavin 11 received a dispersion relation, in which the term 2πM (1 − e −kzd )/k z d replaces the magnetostatic contribution in our dispersion relation (22) …”

Section: Spin Waves In Films Boundary Conditionsmentioning

confidence: 99%

“…Malomed et al 21 solved numerically the GrossPitaevskii equation with added spin pumping and relaxation and found that sometimes asymmetric magnon distributions emerge, but only at asymmetric boundary conditions. Experimentally Nowik-Boltyk et al 22 revealed spatial periodic oscillations of magnon density, which are possible only if magnons condense in the both energy minima.…”

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confidence: 99%

Spin superfluidity and spin waves in YIG films

Sonin

2017

Phys. Rev. B

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Recently it was suggested that stationary spin supercurrents (spin superfluidity) are possible in the magnon condensate observed in yttrium-iron-garnet (YIG) magnetic films under strong external pumping. Here we analyze this suggestion. From topology of the equilibrium order parameter in YIG one must not expect energetic barriers making spin supercurrents metastable. However some small barriers of dynamical origin are possible nevertheless. The critical phase gradient (analog of the Landau critical velocity in superfluids) is proportional to intensity of the coherent spin wave (number of condensed magnons). The conclusion is that although spin superfluidity in YIG films is possible in principle, the published claim of its observation is not justified.The analysis revealed that the widely accepted spin-wave spectrum in YIG films with magnetostatic and exchange interaction required revision. This led to revision of non-linear corrections, which determine stability of the magnon condensate with and without spin supercurrents.

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“…It is also known that such dislocations strongly influence the magnetic dynamics in YIG. 28 Possible mechanisms of the defect-mediated symmetry breaking can include a growth-induced imbalance between clockwise and counter-clockwise screw dislocations in conjunction with a spin-orbit interaction.…”

Section: Fmr Measurementsmentioning

confidence: 99%

Chiral charge pumping in graphene deposited on a magnetic insulator

et al. 2017

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We demonstrate experimentally that a sizable chiral charge pumping can be achieved at room temperature in graphene/Yttrium Iron Garnet (YIG) bilayer systems. The effect, which cannot be attributed to the ordinary spin pumping, reveals itself in the creation of a dc electric field/voltage in graphene as a response to the dynamic magnetic excitations (spin waves) in an adjacent out-of-plane magnetized YIG film. We show that the induced voltage changes its sign when the orientation of the static magnetization is reversed, clearly indicating the broken mirror reflection symmetry about the planes normal to the graphene/YIG interface. The strength of effect shows a non-monotonous dependence on the spin-wave frequency, in agreement with the proposed theoretical model.

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Spatially non-uniform ground state and quantized vortices in a two-component Bose-Einstein condensate of magnons

Cited by 90 publications

References 34 publications

Magnon-magnon interactions in a room-temperature magnonic Bose-Einstein condensate

Magnon-magnon interactions in a room-temperature magnonic Bose-Einstein condensate

Spin superfluidity and spin waves in YIG films

Chiral charge pumping in graphene deposited on a magnetic insulator

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