The Road to the Unitary Bose Gas
type: Dataset
description: Ultracold gases have become versatile systems to study quantum many-body effects. Their high degree of control and the tunability of the atomic interactions led to important advances in the understanding of strongly correlated matter. In the regime of strong interactions, unlike fermions, the study of bosons is hampered by three-particle recombination that leads to atom losses and keeps the system from reaching a real equilibrium state. In this thesis, we have performed the first quantitative comparison between theory and experiment on the three-particle loss coefficient L_3(a,T), for arbitrary scattering length a and temperature T. For unitary two-particle scattering (|a| → ∞), we show that the three-particle loss coefficient follows the law L_3(∞, T ) = λ_3/T^2, that we have tested using a trapped non-degenerate ^{7}Li gas maintained at constant temperature. The measured value of λ_3 = 2.5(3)_{stat}(6)_{cyst} × 10^{−20}(μK)^2cm^6s^{−1} is, within the error bars in good agreement with the theory prediction λ_3^{th} = 1.52 × 10^{−20}(μK)^2cm^6s^{−1}. We have extended our measurements to arbitrary values of the scattering length a. For a < 0, the theory predicts a smooth connection between the previously derived zero-temperature model for L_3(a, 0) and the unitarity limited loss coefficient L_3(∞, T ). We also show that a second Efimov resonance in 7Li should be observable near a = − 500 a0 for a temperature of 1 μK. Finally, we compare our theoretical prediction with measurements performed at Innsbruck with ^{133}Cs and at Cambridge with ^{39}K. The theory also shows remarkable quantitative agreement with these measurements.
issued: 2026-05-06T06:29:48.196269
language: en
modified: 2026-05-06T06:29:48.196274
contact point: Organization
  fn: CCSD
keyword: efimov-physics
keyword: few-particle-physics
keyword: gaz-de-bose-en-interactions-fortes
keyword: gaz-quantiques
keyword: infoeu-reposemanticsdoctoralthesis
keyword: physcondgasphysics-physicscondensed-matter-cond-matquantum-gases-cond-matquant-gas
keyword: physique-a-peu-de-corps
keyword: physique-defimov
keyword: probleme-a-trois-corps
keyword: recombinaison-a-trois-corps
keyword: strongly-interacting-bose-gas
keyword: theses
keyword: three-particle-problem
keyword: three-particle-recombination
keyword: ultracold-gases
landing page: https://theses.hal.science/tel-00951256

The Road to the Unitary Bose Gas
type: Distribution
format: HTML
issued: 2026-05-06T06:29:48.219483
modified: 2026-05-06T06:29:48.169702
access URL: https://theses.hal.science/tel-00951256

test_moissonnage_selune
type: Agent