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Nat Commun. 2014 Mar 11;5:3452. doi: 10.1038/ncomms4452.

Bose-Einstein condensation in an ultra-hot gas of pumped magnons.

Author information

1
Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universit├Ąt Kaiserslautern, 67663 Kaiserslautern, Germany.
2
Department of Physics, Oakland University, Rochester, Michigan 48309, USA.
3
1] Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universit├Ąt Kaiserslautern, 67663 Kaiserslautern, Germany [2] Faculty of Radiophysics, Taras Shevchenko National University of Kyiv, 01601 Kyiv, Ukraine.
4
Faculty of Radiophysics, Taras Shevchenko National University of Kyiv, 01601 Kyiv, Ukraine.

Abstract

Bose-Einstein condensation of quasi-particles such as excitons, polaritons, magnons and photons is a fascinating quantum mechanical phenomenon. Unlike the Bose-Einstein condensation of real particles (like atoms), these processes do not require low temperatures, since the high densities of low-energy quasi-particles needed for the condensate to form can be produced via external pumping. Here we demonstrate that such a pumping can create remarkably high effective temperatures in a narrow spectral region of the lowest energy states in a magnon gas, resulting in strikingly unexpected transitional dynamics of Bose-Einstein magnon condensate: the density of the condensate increases immediately after the external magnon flow is switched off and initially decreases if it is switched on again. This behaviour finds explanation in a nonlinear 'evaporative supercooling' mechanism that couples the low-energy magnons overheated by pumping with all the other thermal magnons, removing the excess heat, and allowing Bose-Einstein condensate formation.

PMID:
24613901
DOI:
10.1038/ncomms4452
[Indexed for MEDLINE]

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