QFS 2016 Book of Abstracts

Abstracts

I5.2 Supercurrent in a room temperature Bose-Einstein magnon condensate Serga Alexander A. Technische Universit¨at Kaiserslautern, Fachbereich Physik and Landesforschungszentrum OPTIMAS, 67663 Kaiserslautern, Germany A supercurrent of magnons is detected by Brillouin light scattering spectroscopy in a magnon Bose-Einstein condensate (BEC) prepared in a room temperature Y 3 F e 5 O 12 magnetic film. The local laser heating induces a frequency shift between different parts of the BEC and leads to an increasing phase gradient in the condensate. As a result, a phase-gradient-induced current – a magnon supercurrent – flowing out of the focal spot, is excited. This efflux reduces the BEC density in the probing point but it does not alter the dynamics of gaseous magnons. I5.3 SQUID detection of Nano-electro-mechanical systems Casey, Andrew(1), Mellor Rupert(1), Lusher, Chris(1), Cowan, Brian(1), Saunders, John(1), Lulla, Kunal(2) 1) Royal Holloway University of London, Physics Department, UK 2) Lancaster University, Physics Department, UK Nano-electro-mechanical systems at low temperatures can form elements of ultra-sensitive detection schemes. The integration of such devices into quantum fluids experiments provides a potential route for studying surface modes and properties of confined superfluids. In this work we investigate how the properties of a NEMs beam are modified by coupling to the input circuit of a remote SQUID, a configuration compatible with ultra-low temperatures. Here modification of the SQUID bias conditions and the magnetic field applied to the NEMs beam effect the strength and sign of the coupling to the SQUID. We demonstrate that the beam can be driven into a stable state of self-sustained oscillations.

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