Phase Diagram for Magnon Condensate in Yttrium Iron Garnet Film

Recently, magnons, which are quasiparticles describing the collective motion of spins, were found to undergo Bose-Einstein condensation (BEC) at room temperature in films of Yttrium Iron Garnet (YIG). Unlike other quasiparticle BEC systems, this system has a spectrum with two degenerate minima, whic...

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Bibliographic Details
Published in:Scientific reports 2013-03, Vol.3 (1), p.1372-1372, Article 1372
Main Authors: Li, Fuxiang, Saslow, Wayne M., Pokrovsky, Valery L.
Format: Article
Language:English
Subjects:
639/301/119/544
639/766/119/2791
639/766/119/2793
639/766/483/640
BOSE-EINSTEIN CONDENSATES
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
Condensation
Energy
FERROMAGNETISM
Humanities and Social Sciences
Iron
Light scattering
multidisciplinary
Physics
Science
Science & Technology - Other Topics
SURFACES, INTERFACES AND THIN FILMS
Temperature effects
THEORETICAL PHYSICS
Thin films
Yttrium
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Summary:Recently, magnons, which are quasiparticles describing the collective motion of spins, were found to undergo Bose-Einstein condensation (BEC) at room temperature in films of Yttrium Iron Garnet (YIG). Unlike other quasiparticle BEC systems, this system has a spectrum with two degenerate minima, which makes it possible for the system to have two condensates in momentum space. Recent Brillouin Light Scattering studies for a microwave-pumped YIG film of thickness d = 5 μm and field H = 1 kOe find a low-contrast interference pattern at the characteristic wavevector Q of the magnon energy minimum. In this report, we show that this modulation pattern can be quantitatively explained as due to unequal but coherent Bose-Einstein condensation of magnons into the two energy minima. Our theory predicts a transition from a high-contrast symmetric state to a low-contrast non-symmetric state on varying the d and H and a new type of collective oscillation.
ISSN:2045-2322
2045-2322
DOI:10.1038/srep01372