Condensed Fraction of an Atomic Bose Gas Induced by Critical Correlations

Abstract

We study the condensed fraction of a harmonically-trapped atomic Bose gas at the critical point predicted by mean-field (MF) theory. The non-zero condensed fraction $f_0$ is induced by critical correlations which increase the transition temperature $T_c$ above $\T_c^{MF}$. Unlike the $T_c$ shift in a trapped gas, $f_0$ is sensitive only to the critical behaviour in the quasi-uniform part of the cloud near the trap centre. To leading order in the interaction parameter $a/{\lambda }_0$, where $a$ is the s-wave scattering length and ${\lambda }_0$ the thermal wavelength, we expect a universal scaling $f_0\propto (a/{\lambda }_0{)}^4$. We experimentally verify this scaling using a Feshbach resonance to tune $a/{\lambda }_0$. Further, using the local density approximation, we compare our measurements with the universal result obtained from Monte-Carlo simulations for a uniform system, and find excellent quantitative agreement.

4 pages, 3 figures

References in corpus (6)

• Many-Body Physics with Ultracold Gases
• Observation of an Efimov spectrum in an atomic system
• Exploring the thermodynamics of a two-dimensional Bose gas
• Effects of Interactions on the Critical Temperature of a Trapped Bose Gas
• Can a Bose gas be saturated?
• Efficient Production of Large 39K Bose-Einstein Condensates

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