tailieunhanh - Phase structure of bose-einstein condensate in ultra - cold bose gases

The Bose - Einstein condensation of ultra - cold Bose gases is studied by means of the Cornwall - Jackiw - Tomboulis effective potential approach in the improved double - bubble approximation which preserves the Goldstone theorem. The phase structure of Bose - Einstein condensate associating with two different types of phase transition is systematically investigated. Its main feature is that the symmetry which was broken at zero temperature gets restored at higher temperature. | Communications in Physics, Vol. 24, No. 4 (2014), pp. 343-351 DOI: PHASE STRUCTURE OF BOSE - EINSTEIN CONDENSATE IN ULTRA COLD BOSE GASES TRAN HUU PHAT Vietnam Atomic Energy Institute, 59 Ly Thuong Kiet, Hanoi, Vietnam LE VIET HOA Department of Physics, Hanoi University of Education, 136 Xuan Thuy, Cau Giay, Hanoi, Vietnam DANG THI MINH HUE Division of Physics, Hanoi Water Resources University, 175 Tay Son, Dong Da, Hanoi, Vietnam E-mail: hue_dtm@ Received 02 October 2014 Accepted for publication 24 December 2014 Abstract. The Bose - Einstein condensation of ultra - cold Bose gases is studied by means of the Cornwall - Jackiw Tomboulis effective potential approach in the improved double - bubble approximation which preserves the Goldstone theorem. The phase structure of Bose - Einstein condensate associating with two different types of phase transition is systematically investigated. Its main feature is that the symmetry which was broken at zero temperature gets restored at higher temperature. Keywords: Bose-Einstein condensation, superfluid and restoration phase transition. I. INTRODUCTION The experiments on Bose - Einstein condensation (BEC) of atomic vapors 87 Rb and 23 Na was successfully realized in 1995 [1, 2]. Just after this first achievement a series of experiments [3], [6] dealing with BEC of systems composed of two distinct species of atoms revealed that the multi - component BEC is not a simple extension of the single component BEC. There arise many fascinating phenomena such as the quantum tunneling of spin domain [7], vortex configuration [8], phase segregation [9] and so on. This event marked a very rapid development in the study of quantum gases. The most attractive feature of all experiments realizing BEC in dilute ultra - cold gases is that almost every parameter of the system is controllable, thereby many novel phenomena, in particular, various types of phase transition, could be created experimentally by