A new Fermi liquid: the normal phase of a strongly interacting gas of cold atoms
Résumé
In 1956 Landau developed an elegant description of interacting Fermi systems at low temperature relying on the existence of long-lived quasiparticles. While this Fermi liquid theory (FLT) describes well Helium 3 and many solidstate materials above the superfluid temperature, there exist notable exceptions such as underdoped cuprates [1]. In dilute atomic fermionic gases, the Fermi liquid nature of the normal phase is currently under debate. On the one hand, recent photoemission spectroscopy experiments near the critical temperature were interpreted using a pseudogap model [2]. On the other hand, measurement of the temperature dependence of the specific heat displayed a linear behaviour compatible with Fermi liquid's prediction [3]. Here, we measure the magnetic susceptibility of a Fermi gas with tunable interaction in the low temperature limit and compare it to quantum Monte Carlo calculations. Experiment and theory are in excellent agreement and fully compatible with FLT. We also measure the condensation energy which is a key quantity measured in superconducting compounds. Temperature variation data and magnetic susceptibility are combined to deduce a full set of Fermi liquid parameters describing the microscopic quasiparticle properties of the normal phase. The photoemission spectrum calculated with these parameters is found in good agreement with the measurements reported in [2]. We conclude that all existing data to date on the normal phase of the unitary Fermi gas are well described by Landau's Fermi liquid theory.
Domaines
Gaz Quantiques [cond-mat.quant-gas]
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