Finite-range effects in ultradilute quantum drops

Abstract

In the first experimental realization of dilute Bose-Bose liquid drops using two hyperfine states of 39 K some discrepancies between theory and experiment were observed. The standard analysis of the data using the Lee-Huang-Yang beyond mean-field theory predicted critical numbers which were significantly off the experimental measurements. Also, the radial size of the drops in the experiment proved to be larger than expected from this theory. Using a new functional, which is based on quantum Monte Carlo results of the bulk phase incorporating finite-range effects, we can explain the origin of the discrepancies in the critical number. This result proves the necessity of including finite-range corrections to deal with the observed properties in this setup. The controversy on the radial size is reasoned in terms of the departure from the optimal concentration ratio between the two species of the mixture. arXiv:2001.09086v1 [cond-mat.quant-gas]

Beyond Lee-Huang-Yang description of self-bound Bose mixtures

“…[3] we introduce the rescaled coordinater = r/ξ with ξ = 6ħ h 2 /(|δg|mn 0 ), where the equilibrium density n 0 is given in Eq. (13). Then, the energy functional associated to the equation of state (6) with the beyond Bogoliubov speed of sound (11) is written as…”

“…[3] for the metastable state (= 22.55), the confined geometry measurement showed a deviation of N c to lower value. Recently, this deviation was accounted for the effects of finite-range in the interaction potential, which is neglected in the contact type s-wave description [12,13].…”

“…[9]. In this regard, theoretical works based on beyond mean-field variational [12] and QMC [13] approaches pointed out the crucial role played by finite-range effects. Recently, many theoretical works have been devoted to the investigation of the liquid phase in low-dimensional systems, motivated by the enhanced role of quantum fluctuations [14][15][16].…”

“…Equation of state in units of the equilibrium density(13) and energy(12), for different values of δg/g. The lowest black solid line is the universal result from Ref [3]…”

Many-body and temperature effects in two-dimensional quantum droplets in Bose–Bose mixtures

“…In addition, it fails to properly predict the critical atom number 20 , 23 and to describe effects of quantum correlations 23 . In this regard, many theoretical works beyond the generalized GPE have been introduced to study the properties of self-bound droplets 19 – 22 , 24 – 28 . Among them, the pairing theory 19 which has been used in order to improve the Petrov’s theory 13 for quantum droplets of 2D Bose mixtures.…”