Regensburg 2010 – scientific programme
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MA: Fachverband Magnetismus
MA 26: Spin Dynamics / Spin Torque IV
MA 26.3: Talk
Thursday, March 25, 2010, 15:00–15:15, H10
Time-resolved and wave-vector sensitive observation of a pump-free BEC — •Christian W. Sandweg1, Alexander A. Serga1, Vitaliy I. Vasyuchka1, Andrii V. Chumak1, Timo Neumann1, Björn Obry1, Helmut Schultheiss1, Gennadii A. Melkov2, Andrei N. Slavin3, and Burkard Hillebrands1 — 1FB Physik and Landesforschungszentrum OPTIMAS, TU Kaiserslautern, 67663 Kaiserslautern, Germany — 2Department of Radiophysics, National Taras Shevchenko University of Kiev, Ukraine — 3Department of Physics, Oakland University, Rochester, MI, USA
We report on the temporal and wave-vector sensitive investigation of a pump-free Bose-Einstein-Condensate (BEC) of magnons at room temperature. To create the condensate the technique of parametric microwave pumping is used. A microwave photon splits into two magnons with half of the pumping frequency and opposite k-vector. In a competing process only the group of magnons at half of the pumping frequency having the lowest damping survives. The magnons of this dominant group (DG) thermalize to the lowest energy state and a BEC of magnons is formed. The DG not only plays the role of an energy source for the BEC but is in the same time the most important disruptive factor for it. When the pumping is switched off the BEC of magnons can freely evolve which result in a strong increase of intensity of the condensate on the same time scale as the dominant group decays. To separate the BEC dynamics from the evolution of the other components of the magnon gas near the lowest energy state, time-resolved measurements were performed in combination with wave-vector sensitivity.