Bose-Einstein condensation of quasi-equilibrium magnons at room temperature under pumping

Bose-Einstein condensation is one of the most fascinating phenomena predicted by quantum mechanics. It involves the formation of a collective quantum state composed of identical particles with integer angular momentum (bosons), if the particle density exceeds a critical value. To achieve Bose-Einste...

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Bibliographic Details
Published in:Nature 2006-09, Vol.443 (7110), p.430-433
Main Authors: DEMOKRITOV, S. O, DEMIDOV, V. E, DZYAPKO, O, MELKOV, G. A, SERGA, A. A, HILLEBRANDS, B, SLAVIN, A. N
Format: Article
Language:English
Subjects:
Bosons
Chemical potential
Classical and quantum physics: mechanics and fields
Condensation
Condensing
Density
Energy
Exact sciences and technology
Excitation
Experiments
Flow rates
High temperature
Magnetism
Magnons
Matter waves
Physics
Pumping
Quantum theory
Spin waves
Temperature
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Summary:Bose-Einstein condensation is one of the most fascinating phenomena predicted by quantum mechanics. It involves the formation of a collective quantum state composed of identical particles with integer angular momentum (bosons), if the particle density exceeds a critical value. To achieve Bose-Einstein condensation, one can either decrease the temperature or increase the density of bosons. It has been predicted that a quasi-equilibrium system of bosons could undergo Bose-Einstein condensation even at relatively high temperatures, if the flow rate of energy pumped into the system exceeds a critical value. Here we report the observation of Bose-Einstein condensation in a gas of magnons at room temperature. Magnons are the quanta of magnetic excitations in a magnetically ordered ensemble of magnetic moments. In thermal equilibrium, they can be described by Bose-Einstein statistics with zero chemical potential and a temperature-dependent density. In the experiments presented here, we show that by using a technique of microwave pumping it is possible to excite additional magnons and to create a gas of quasi-equilibrium magnons with a non-zero chemical potential. With increasing pumping intensity, the chemical potential reaches the energy of the lowest magnon state, and a Bose condensate of magnons is formed.
ISSN:0028-0836
1476-4687
1476-4679
DOI:10.1038/nature05117