Berlin 2015 – scientific programme
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MA: Fachverband Magnetismus
MA 43: Magnetization / Demagnetization Dynamics III
MA 43.2: Talk
Thursday, March 19, 2015, 09:45–10:00, EB 301
Full electric detection of a Bose-Einstein condensate via the spin-pumping effect — •Dmytro A. Bozhko1,2, Akihiro Kirihara3, Andrii V. Chumak1, Gennadii A. Melkov4, Yaroslav Tserkovnyak5, Burkard Hillebrands1, and Alexander A. Serga1 — 1Fachbereich Physik and Landesforschungszentrum OPTIMAS, TU Kaiserslautern, Germany — 2Graduate School Materials Science in Mainz, Germany — 3Smart Energy Research Laboratories, NEC Corporation, Japan — 4Faculty of Radiophysics, Taras Shevchenko National University of Kyiv, Ukraine — 5Department of Physics and Astronomy, University of California, USA
It is well known, that magnons excited in an insulating magnetic medium can transfer their angular momenta to free electrons in an adjacent non-magnetic metal layer, and thus generate a spin current via the spin-pumping effect. Due to the inverse spin Hall effect (ISHE) this current is transformed into a charge current and is measured as an electric voltage. It is commonly believed that the magnitude of the ISHE voltage increases with the total number of magnons in a spin-wave system as well as with the energy of these magnons. However, the electric signal, which corresponds to the formation of a magnon Bose-Einstein condensate (BEC) by a freely evolving magnon gas after the termination of an external pumping, breaks with this rule: The transition of the thermalized gaseous magnons to the lowest energy states leads to a pronounced upward jump of the voltage magnitude. This unusual behaviour can be understood as a result of a rectification of a coherent microwave current induced by the coherence of the BEC.