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Q: Fachverband Quantenoptik und Photonik

Q 14: Ultra-cold atoms, ions and BEC II (with A)

Q 14.5: Vortrag

Montag, 18. März 2013, 15:00–15:15, F 428

Measurements on first and second sound in a unitary Fermi gas — •Leonid A. Sidorenkov^1,2, Meng Khoon Tey^1,2, Rudolf Grimm^1,2, Yan-Hua Hou³, Lev Pitaevskii^3,4, and Sandro Stringari³ — ¹Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria — ²Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria — ³Dipartimento di Fisica, Universitá di Trento and INO-CNR BEC Center, 38123 Povo, Italy — ⁴Kapitza Institute for Physical Problems RAS, 119334 Moscow, Russia

We report on the propagation of first- and second-sound-like excitations in a highly elongated Fermi gas with unitarity-limited interactions around the critical temperature for superfluidity. Our measurements on first sound are in excellent agreement with calculations based on the recently measured equation of state (EoS) of the unitary Fermi gas for the whole temperature range explored. Given the available knowledge of thermodynamic quantities from the EoS, we investigate second-sound-like excitations in the unitary Fermi gas, and their connection to the superfluid hydrodynamics. Observation of these second-sound-like excitations offers, in analogy to superfluid helium, a direct access to the local superfluid density. This quantity cannot be obtained in EoS measuremens and requires additional knowledge of the elementary excitation spectrum of the unitary Fermi gas.