Universal quantum effect of two-body correlation in a weakly interacting Bose gas

Abstract

Based on the Cornwall-Jackiw-Tomboulis (CJT) effective action approach and the requirement to preserve the Goldstone theorem within two-loop approximation, we study the universal quantum effect, which is related to the two-body correlation, in a homogeneous weakly interacting Bose gas at zero temperature. We find the state equations that provide the condensate fraction, energy density, chemical potential, and sound speed. They are the series expansions of the gas parameter.

Quantum fluctuation in the segregation phase of two-component weakly interacting Bose–Einstein condensates

“…Equations (34) and (35) are the same as the results of a single BEC with the homogeneous atomic density is ρ j [22]. They become exactly like the famous results of Lee-Huang-Yang in [20] when keeping the leading term of the gas parameter.…”

“…By defining the effective potential chemical as equation (19), we develop the pressure balance condition of two phases in [8] as equation (20), which leads to the appearance of  j in the SD equation (23) that characters the influence between two condensates. It shows that considering the segregation phase in two-component Bose gases of this work is not simply a direct extension of our previous work in [22].…”

“…The experimental observation was reported in [21]. Recently, the results of Lee-Huang-Yang were reconfirmed by using the CJT theory [22]. To the leading order of the gas parameter, the excited fraction of a single BEC increases as the power 3/2 of the repulsive interaction strength between atoms.…”

“…This paper reports the properties of the excited and condensed fractions of a three-dimensional segregated BECs in non-confined space, including the two-body correlation universal quantum effect, based on the GP theory and CJT effective action approach. Interestingly, our results show that the atomic interaction leads to the local feature, and also decreases the quantum fluctuation instead of the homogeneous feature, and only increasing of single BEC [20,22] or miscible BECs [23]. The paper is structured as follows: In section 2, the segregation phase of BECs is described based on the condensate density profiles within the double parabola approximation (DPA) of the GP theory.…”