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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.
130