Quantum Optics Seminar by Doerte Blume – Niels Bohr Institute - University of Copenhagen

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Quantum Optics Seminar by Doerte Blume

The properties of two-component Fermi gases become universal if the interspecies s-wave scattering length and the average interparticle spacing are much larger than the range of the underlying two-body potential.

This talk summarizes some of our recent zero- and finite-temperature calculations of small two-component Fermi gases under external harmonic confinement. Using the path integral Monte Carlo approach, we determine the Tan contact for infinitely large s-wave scattering length, i.e., at  unitarity. We find that the path integral Monte Carlo approach yields reliable results down to below the "Fermi temperature"; at very low temperature, however, the Fermi sign problem renders the simulations impossible. The path integral Monte Carlo results compare favorably with results obtained by performing the thermal average explicitly. We also determine the superfluid fraction and local superfluid density, which are defined in terms of the moment of inertia, of small two-component Fermi gases as functions of the temperature and the s-wave scattering length.

For spin-imbalanced systems, the superfluid fraction at low temperature exhibits an intriguing dependence on the s-wave scattering length.