QFS 2016 Book of Abstracts

Abstracts

P4.30 Higgs mode in a trapped superfluid Fermi gas Jun Tokimoto(1), Shunji Tsuchiya(2), Tetsuro Nikuni(1) 1) Tokyo University of Science, Faculty of Science, Department of Physics, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan 2) Tohoku Institute of Technology, 35-1 Yagiyamakasumicho, Taihaku-ku, Sendai-shi, Miyagi 982-8577, Japan In quantum many-body systems with spontaneous breaking of a continuous symmetry, Higgs modes emerge as collective amplitude oscillations of order parameters. Recently, Higgs modes have been observed in superconductors and for in Bose gases in optical lattices. But, it has not yet been observed in Fermi gases. In this study, we use the time-dependent Bogoliubov-de Gennes equations to investigate Higgs amplitude oscillations of the superfluid order parameter in a trapped Fermi gas induced by a sudden changes of the s-wave scattering length. In particular, we discuss how the frequency and damping of the Higgs mode changes as one goes from BCS regime to BEC regime. P4.31 Platform for ultra-low temperature transport measurements on low-dimensional electron systems Lev Levitin(1), Harriet van der Vliet(1), John H. Quilter(1), Antonio C´orcoles(1,4), Spas Spasov(1,5), Graham Creeth(2), Ian Farrer(3,6), David Ritchie(3), Jan Ny´eki(1), Andrew Casey(1), James Nicholls(1), John Saunders(1) 1) Department of Physics, Royal Holloway, University of London, UK 2) Department of Physics and Astronomy, University College London and London Centre for Nanotechnology, UK 3) Department of Physics, University of Cambridge, UK 4) now at IBM Watson Center, Yorktown Heights, NY, USA 5) now at Ionoptika, Southampton, UK 6) now at Department of Electronic and Electrical Engineering, University of Sheffield, UK We present work on cooling a two-dimensional electron gas (2DEG) in a GaAs-AlGaAs quantum well to ultra-low temperature. We cool the 2DEG via Ohmic contacts thermalised to blocks of silver sinter in a 3 He immersion cell mounted on a nuclear demagnetisation cryostat. The electron temperature is measured with a noise thermometer coupled via an additional Ohmic contact. We derive a thermal model that links the temperatures of 2DEG and noise thermometer with heat flow in the cell, and confirm this model experimentally. So far we have cooled 2DEG below 3 mK, under a measured ≈ 30 fW heat leak. Improved electrical filters should reduce these values and take the 2DEG into the microkelvin regime.

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