Pantheon SEMPARIS Le serveur des séminaires parisiens Paris

Status Confirmed
Seminar Series SEM-LPTM-UCP
Subjects cond-mat
Date Thursday 11 May 2017
Time 14:00
Institute LPTM
Seminar Room 4.13 St Martin II
Speaker's Last Name Clement
Speaker's First Name David
Speaker's Email Address
Speaker's Institution Laboratoire Charles Fabry, Institut d'Optique, Palaiseau
Title Single-atom- and momentum-resolved investigation of the condensate depletion in interacting Bose gases.
Abstract The interplay of quantum fluctuations and interaction is at the core of intriguing phenomena of quantum many-body physics. An emblematic example, conceptually rather simple, of such a manifestation is the quantum depletion of a Bose condensate occurring at zero temperature. The resulting many-body ground-state, a vacuum of quasi-particles, is composed of single-particle excitations on top of the condensate, for which a direct observation has been missing. I will report on the single-atom-resolved measurement of the distribution of momenta k in interacting Bose gas of metastable Helium after a 330 ms Time-Of-Flight (TOF). We investigate two different potentials where atoms are trapped before being released. In a 3D harmonic trap, we monitor the TOF distribution at various temperatures and clearly separate and identify, by their k-dependence, two distinct contributions to the depletion of the condensate: the thermal and the quantum depletion [1]. In a 3D optical lattice, we show that the measured TOF distributions are in the far-field regime of expansion, an original configuration that allows us to precisely determine the temperature and the condensed fraction of lattice superfluids. [1] R. Chang et al. Phys. Rev. Lett. 117, 235303 (2016).
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