Nonequilibrium Bose-Einstein condensation of hot magnons

Vannucchi, Fabio Stucchi; Vasconcellos, Áurea R.; Luzzi, Roberto

doi:10.1103/physrevb.82.140404

Cited by 9 publications

(21 citation statements)

References 27 publications

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“…The thermal bath is constituted by the phonon system, with which a nonlinear interaction exists, and the magnons are driven arbitrarily out of equilibrium by a source of electromagnetic radio frequency [21]. Technological applications are related to the construction of sources of coherent microwave radiation [22,23].…”

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confidence: 99%

Dynamics of a Bose-Einstein condensate of excited magnons

2013

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Abstract. The emergence of a non-equilibrium Bose-Einstein-like condensation of magnons in rf-pumped magnetic thin films has recently been experimentally observed. We present here a complete theoretical description of the non-equilibrium processes involved. It it demonstrated that the phenomenon is another example of the presence of a Bose-Einstein-like condensation in nonequilibrium many-boson systems embedded in a thermal bath, better referred-to as Fröhlich-Bose-Einstein condensation. The complex behavior emerges after a threshold of the exciting intensity is attained. It is inhibited at higher intensities when the magnon-magnon interaction drives the magnons to internal thermalization. The observed behavior of the relaxation to equilibrium after the end of the pumping pulse is also accounted for and the different processes fully described.

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confidence: 99%

Dynamics of a Bose-Einstein condensate of excited magnons

2013

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“…In other words, the energy pumped into the system instead of being redistributed among the magnons in such non‐thermal conditions is transferred to the mode that is lowest in frequency (with a fraction of course being dissipated to the surrounding media). Such a phenomenon has been referred to as a non‐equilibrium Bose–Einstein condensation, and we have shown it to be an additional case of NEBEC …”

Section: Several Particular Cases Of Nebecmentioning

confidence: 72%

“…">A fourth case is the case of magnons . The thermal bath is constituted by the phonon system, with which a nonlinear interaction exists, and the magnons are driven arbitrarily out of equilibrium by a source of electromagnetic radio frequency . Technological applications are related to the construction of sources of coherent microwave radiation …”

Section: Introductionmentioning

confidence: 99%

Non‐Equilibrium Bose–Einstein‐Like Condensation

2018

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The original Bose–Einstein condensation (BEC) was theoretically established in the 1920s, for the case of an ideal gas of boson particles (a consequence of the symmetry of the wave function). In the 1990s, it was realized in systems of atomic alkali gases. At the beginning of the 21st century, investigators considered its emergence in solid‐state matter, and a BEC‐like phenomenon was observed in the case of bosonic quasiparticles (elementary excitations in solids). Both types of BEC can occur in a condensation in conditions of thermodynamic equilibrium. A third type of what has been dubbed a BEC in non‐equilibrium conditions can occur in systems of bosonic quasiparticles (phonons, magnons, excitons); this phenomenon (which can be considered as cases of systems with complex behavior) follows after a certain threshold of intensity of an external pumping source is achieved. In this review, after brief comments on the two types of BEC in equilibrium, a description is presented on how a BEC‐like phenomenon arises in systems of quasiparticles that are driven away from thermodynamic equilibrium, and several examples are described. This description is given within a unique theoretical framework, and a comparison with experimental results is performed; in addition, the possible technological applications are outlined.

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“…[7], we could tune the magnitude of the phase in the cosine function of Eq. (27) and consequently, we might control the direction of the dc magnon current. …”

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confidence: 99%

Magnon transport through microwave pumping

2015

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We present a microscopic theory of magnon transport in ferromagnetic insulators (FIs). Using magnon injection through microwave pumping, we propose a way to generate magnon dc currents and show how to enhance their amplitudes in hybrid ferromagnetic insulating junctions. To this end focusing on a single FI, we first revisit microwave pumping at finite (room) temperature from the microscopic viewpoint of magnon injection. Next, we apply it to two kinds of hybrid ferromagnetic insulating junctions. The first is the junction between a quasi-equilibrium magnon condensate and magnons being pumped by microwave, while the second is the junction between such pumped magnons and noncondensed magnons. We show that quasi-equilibrium magnon condensates generate ac and dc magnon currents, while noncondensed magnons produce essentially a dc magnon current. The ferromagnetic resonance (FMR) drastically increases the density of the pumped magnons and enhances such magnon currents. Lastly, using microwave pumping in a single FI, we discuss the possibility that a magnon current through an Aharonov-Casher phase flows persistently even at finite temperature. We show that such a magnon current arises even at finite temperature in the presence of magnon-magnon interactions. Due to FMR, its amplitude becomes much larger than the condensed magnon current.

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Nonequilibrium Bose-Einstein condensation of hot magnons

Cited by 9 publications

References 27 publications

Dynamics of a Bose-Einstein condensate of excited magnons

Dynamics of a Bose-Einstein condensate of excited magnons

Non‐Equilibrium Bose–Einstein‐Like Condensation

Magnon transport through microwave pumping

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