Department of Physics, Engineering Physics & Astronomy

Department of Physics, Engineering Physics & Astronomy
Department of Physics, Engineering Physics & Astronomy

Measurements of a Bose-Einstein Condensate at Finite Temperature

Joseph Thywissen
Department of Physics, University of Toronto

Wednesday, March 3, 2004
10:30 AM @ Stirling 501

Abstract:

We have investigated experimentally the finite-temperature properties of a Bose-Einstein condensed cloud of 87Rb atoms in a harmonic trap. Focusing primarily on condensed We have investigated experimentally the finite-temperature properties of a Bose-Einstein condensed cloud of 87Rb atoms in a harmonic trap. Focusing primarily on condensed fraction and expansion energy, we measure unambiguous deviations from ideal-gas thermodynamics. Our results offer for the first time clear evidence of the mutual interaction between the condensed and thermal components.

To probe the low-temperature region inaccessible to the usual time-of-flight technique, we use coherent Bragg scattering as a filtering technique for the condensate. This allows us to separate spatially the condensed and normal components in time of flight, and to measure reliably temperatures as low as 0.2 T_c and thermal fractions as low as 10%.

Comparisons with predictions of a Hartree-Fock description of the mixed cloud provide evidence for the limitations of the usual assumptions about mixed clouds after a time of flight expansion, pointing out to the need for a further theoretical work.