Momentum distribution of 1D Bose gases at the quasi-condensation crossover: theoretical and experimental investigation

Thibaut Jacqmin (1) , Bess Fang (1) , Tarik Berrada (1) , Tommaso Roscilde (2) , Isabelle Bouchoule (1)

1 Laboratoire Charles Fabry / Optique atomique
2 Phys-ENS - Laboratoire de Physique de l'ENS Lyon

We investigate the momentum distribution of weakly interacting 1D Bose gases at thermal equilibrium both experimentally and theoretically. Momentum distribution of single 1D Bose gases is measured using a focusing technique, whose resolution we improve via a levitation scheme. The momentum distribution compares very well with quantum Monte Carlo calculations for the Lieb-Liniger model at finite temperature, allowing for an accurate thermometry of the gas that agrees with (and improves upon) the thermometry based on in situ density fluctuation measurements. The quasi-condensation crossover is investigated via two different experimental situations, each lying on either side of the crossover. Classical field theory is expected to correctly describe the quasi-condensation crossover of weakly interacting gases. We derive the condition of validity of the classical field theory, and find that, in typical experiments, interactions are too strong for classical field to be accurate. This is confirmed by a comparison between the classical field predictions and the exact quantum Monte Carlo results.

Mots clés: one-dimensional Bose gas; momentum distribution; Lieb-Liniger model; quantum Monte Carlo calculation; classical field approximation

Domaines: Gaz Quantiques [cond-mat.quant-gas]

Thibaut Jacqmin, Bess Fang, Tarik Berrada, Tommaso Roscilde, Isabelle Bouchoule. Momentum distribution of 1D Bose gases at the quasi-condensation crossover: theoretical and experimental investigation. 2012. ⟨hal-00716881v1⟩