2017/07/26 by A. E. Golomedov, Yu. E. Lozovik, G. E. Astrakharchik +1
Physics and Astronomy · #Atomic physics #Biexciton #Boson #Cold Atom Physics and Bose-Einstein Condensates #Condensed matter physics #Diffusion Monte Carlo #Exciton #Ground state #Monte Carlo method #Physics #Physics of Superconductivity and Magnetism #Quantum electrodynamics #Quantum mechanics #Quantum, superfluid, helium dynamics #Scattering #Scattering length #cond-mat.quant-gas
paper · pdf · doi:10.1007/s10909-017-1814-y
published as J Low Temp Phys 189, 300 (2017) · 12 pages, 4 figures
arxiv created 2017/07/26 · openalex publication_date 2017/10/13 · arxiv updated 2018/04/20 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Ground state properties of a fermionic Coulomb gas are calculated using the fixed-node diffusion Monte Carlo method. The validity of the composite boson description is tested for different densities. We extract the exciton-exciton s-wave scattering length by solving the four-body problem in a harmonic trap and mapping the energy to that of two trapped bosons. The equation of state is consistent with the Bogoliubov theory for composite bosons interacting with the obtained s-wave scattering length. The perturbative expansion at low density has contributions physically coming from (a) exciton binding energy, (b) mean-field Gross-Pitaevskii interaction between excitons, (c) quantum depletion of the excitonic condensate (Lee-Huang-Yang terms for composite bosons). In addition, for low densities we find a good agreement with the Bogoliubov bosonic theory for the condensate fraction of excitons. The equation of state in the opposite limit of large density is found to be well described by the perturbative theory including (a) mixture of two ideal Fermi gases (b) exchange energy. We find that for low densities both energetic and coherent properties are correctly described by the picture of composite bosons (excitons).