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Superfluidity spotted in Fermi gas

Research groups in the US and Austria say that they have found the best evidence to date for superfluidity – the flow of a fluid without resistance – in a Fermi gas made of ultracold lithium-6 atoms.

Physics WorldMay 1, 20040 citations

A Two-Dimensional Fermi Gas in the BEC-BCS Crossover

M. G. Ries

This thesis reports on the preparation of a 2D Fermi gas in the BEC-BCS crossover and \nthe observation of the BKT transition into a quasi long-range ordered superﬂuid phase. \nThe pair momentum distribution of the gas is probed by means of a matter-wave \nfocusing technique which relies on time-of-ﬂight evolution in a weak harmonic potential. \nThis distribution holds the coherence properties of the gas. \nThe quasi long-range ordered phase manifests itself as a sharp low-momentum peak. \nThe temperature where it forms is identiﬁed as the transition temperature. By tuning \nthe temperature and the interaction strength, the phase diagram of the 2D Fermi gas in \nthe BEC-BCS crossover is mapped out. \nThe phase coherence is investigated in a self-interference experiment. Furthermore, \nalgebraic decay of correlations is observed in the trap average of the ﬁrst order corre- \nlation function, which is obtained from the Fourier transform of the pair momentum \ndistribution. This is in qualitative agreement with predictions of homogeneous theory \nfor the superﬂuid phase in a 2D gas. \nThe presented results provide a foundation for future experimental and theoretical \nstudies of strongly correlated 2D Fermi gases. They might thus help to elucidate complex \nsystems such as the electron gas in high-Tc superconductors.This thesis reports on the preparation of a 2D Fermi gas in the BEC-BCS crossover and \nthe observation of the BKT transition into a quasi long-range ordered superﬂuid phase. \nThe pair momentum distribution of the gas is probed by means of a matter-wave \nfocusing technique which relies on time-of-ﬂight evolution in a weak harmonic potential. \nThis distribution holds the coherence properties of the gas. \nThe quasi long-range ordered phase manifests itself as a sharp low-momentum peak. \nThe temperature where it forms is identiﬁed as the transition temperature. By tuning \nthe temperature and the interaction strength, the phase diagram of the 2D Fermi gas in \nthe BEC-BCS crossover is mapped out. \nThe phase coherence is investigated in a self-interference experiment. Furthermore, \nalgebraic decay of correlations is observed in the trap average of the ﬁrst order corre- \nlation function, which is obtained from the Fourier transform of the pair momentum \ndistribution. This is in qualitative agreement with predictions of homogeneous theory \nfor the superﬂuid phase in a 2D gas. \nThe presented results provide a foundation for future experimental and theoretical \nstudies of strongly correlated 2D Fermi gases. They might thus help to elucidate complex \nsystems such as the electron gas in high-Tc superconductors.

Jan 1, 20151 citation

Condensate made on space station

Edwin Cartlidge

A Bose–Einstein condensate has been created on the International Space Station, which could pave the way for an accurate measurement of gravity, as Edwin Cartlidge reports

Physics WorldAug 1, 20200 citations

Images of Vortices Reveal Superfluidity in a Fermi Gas

Barbara Goss Levi

The superfluid formed in a low-density atomic gas is a clean and controllable system for exploring strong interactions among particles.

Physics TodayJul 1, 20052 citations

Counting weapons – without counting

Edwin Cartlidge

A new technique allows warheads to be authenticated without giving away any details about them, as Edwin Cartlidge reports.

Physics WorldAug 1, 20140 citations

Seeing the Superfluid Transition of a Gas

W. Zwerger

The universal thermodynamic functions of a superfluid formed from a fermion gas of strongly interacting lithium atoms have been measured precisely.