Физика Низких Температур: Том 27, Выпуск 9-10 (Сентябрь 2001), c. 1179-1182    ( к оглавлению , назад )

Real-space condensation in a dilute Bose gas at low temperature

I. O. Kulik

Department of Physics, Bilkent University, Bilkent, Ankara 06533, Turkey
E-mail: kulik@fen.bilkent.edu.tr

Received May 16, 2001


We show with a direct numerical analysis that a dilute Bose gas in an external potential - which is choosen for simplicity as a radial parabolic well - undergoes at certain temperature Tc a phase transition to a state supporting macroscopic fraction of particles at the origin of the phase space (r=0,p=0). Quantization of particle motion in a well wipes out sharp transition but supports a distribution of radial particle density r(r) peacked at r=0 (a real-space condensate) as well as the phase-space Wigner distribution density W(r, p) peaked at r=0 and p=0 below the crossover temperature Tc* of order of Tc. Fixed-particle-number canonical ensemble which is a combination of the fixed-N condensate part and the fixed-m excitation part is suggested to resolve the difficulty of large fluctuation of the particle number (dN~N) in the Bose-Einstein condensation problem treated within the orthodox grand canonical ensemble formalism.

64.60.-i - General studies of phase transitions (see also 63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions; for critical phenomena in solid surfaces and interfaces, and in magnetism, see 68.35.Rh, and 75.40.-s, respectively)