Finite Temperature Excitations of an anisotropically trapped Bose gas : A diffusion Monte Carlo study

Zeyuan Shao, Yi Ping Tang

徹郎 二国

Krešimir Dželalija, Viktor Cikojević, Jordi Boronat +1 more

We study thermal properties of a trapped Bose-Bose mixture in a dilute regime using quantum Monte Carlo methods. Our main aim is to investigate the dependence of the superfluid density and the condensate fraction on temperature for the mixed and separated phases. To this end we use the diffusion Monte Carlo method in the zero-temperature limit and the path-integral Monte Carlo method for finite temperatures. The results obtained are compared with solutions of the coupled Gross-Pitaevskii equations for the mixture at zero temperature. We notice the existence of an anisotropic superfluid density in some phase-separated mixtures. Our results also show that the temperature evolution of the superfluid density and condensate fraction is slightly different, showing noteworthy situations where the superfluid fraction is smaller than the condensate fraction.

S. DATTA

We investigate the thermodynamic properties of a trapped Bose gas of Rb atoms interacting through a repulsive potential at low but finite temperature (kBT < μ < Tc) by Quantum Monte Carlo method based upon the generalization of Feynman-Kac method1-3 applicable to many-body systems at T=0 to finite temperatures. In this paper, we report temperature variation of condensation fraction, chemical potential, density profile, total energy of the system, release energy, frequency shifts and moment of inertia within the realistic potential model (Morse type) for the first time by diffusion Monte Carlo technique. The most remarkable success was in achieving the same trend in the temperature variation of frequency shifts as was observed in JILA4 for both m=2 and m=0 modes. For other things, we agree with the work of Giorgini et al.,5 Pitaevskii et al.6 and Krauth.7

Avy Soffer, Minh-Binh Tran

Huang Wu, E. Arimondo

We analyze the expansion process of a thermal trapped gas taking place during the detection of Bose-Einstein condensation through an expansion of the condensate. By extending our Monte Carlo method to study this phenomenon, we demonstrate that the velocity distributions of the thermal trapped atoms are anisotropic due to anisotropic explosion of atoms. The radial and axial components of translational temperature are different from the trap temperature and have opposite evolution tendencies with the gas expansion.