Mixture Of Bose Gases Research Articles

Large-N Expansion for Condensation and Stability of Bose–Bose Mixtures at Finite Temperatures

The two-component mixture of Bose particles with short-range pairwise interaction at finite temperatures in three dimensions is considered. Particularly we examine, by means of the large-$N$ expansion technique, the stability of mixed state below the Bose-Einstein transition point and the temperature dependence of the condensate density for symmetric mixture of Bose gases. The presented analysis reveals the importance of finite-temperature excitations of the non-condensed particles in formation of the phase diagram of two-component Bose systems.

Faraday waves and droplets in quasi-one-dimensional Bose gases

Faraday waves (FW) are studied in mixtures of Bose gases by taking into account quantum fluctuations beyond the GP mean-field formalism with the Lee-Huang-Yang term, with both inter-and intra-species scattering lengths periodically varying in time. In this case, the effect of periodic modulations on the system is studied, with nonlinear resonances shown to be excited in the oscillation widths of quantum droplets. It was shown that the period of the Faraday patterns is quite sensitive to the estimated value obtained by the beyond mean-field contribution, which can be used to measure quantum fluctuations in the ground state of the quasi-one-dimensional mixture. Variational predictions are confirmed by full numerical simulations. We also add an analysis of quantum droplets and quantum fluctuation contributions when considering three-body interactions.

Faraday waves and droplets in quasi-one-dimensional Bose gas mixtures

Faraday waves in mixtures of Bose gases are studied by taking into account quantum fluctuations beyond the Gross–Pitaevskii mean-field formalism with the Lee–Huang–Yang term. For that, a Bose–Einstein condensed binary atomic mixture is assumed trapped in cigar-type geometry, having the inter- and intra-species scattering lengths periodically varying in time. The period of the Faraday patterns is shown to be quite sensitive to the estimated value obtained by the beyond mean-field contribution, which can be used to measure quantum fluctuations in the ground state of the quasi-one-dimensional mixture. By studying the influence of the above nonlinear periodic modulations on quantum droplet dynamics, we also show that nonlinear resonances are excited in the oscillation widths of the quantum droplets. Variational predictions confirm numerical simulations for the corresponding formalism.

Ground state energy of mixture of Bose gases

We consider the asymptotic behavior of a system of multi-component trapped bosons, when the total particle number [Formula: see text] becomes large. In the dilute regime, when the interaction potentials have the length scale of order [Formula: see text], we show that the leading order of the ground state energy is captured correctly by the Gross–Pitaevskii energy functional and that the many-body ground state fully condensates on the Gross–Pitaevskii minimizers. In the mean-field regime, when the interaction length scale is [Formula: see text], we are able to verify Bogoliubov’s approximation and obtain the second order expansion of the ground state energy. While such asymptotic results have several precursors in the literature on one-component condensates, the adaptation to the multi-component setting is non-trivial in various respects and the analysis will be presented in detail.

Liquid beyond the van der Waals paradigm

An ultracold mixture of Bose gases is eight orders of magnitude more dilute than water. However, quantum fluctuations turn it into a self-bound liquid droplet.

Derivation of the Hartree equation for compound Bose gases in the mean field limit

We consider mixtures of Bose gases of different species. We prove that in the mean field limit and under suitable conditions on the initial condition, a system composed of two Bose species can be effectively described by a system of coupled Hartree equations. Moreover, we derive quantitative bounds on the rates of convergence of the reduced density matrices in Sobolev trace norms. We treat both the non-relativistic case in the presence of an external magnetic field [Formula: see text] and the semi-relativistic case.

Phase Transition in Binary Mixture of Bose Gases

Based on the Cornwall-Jackiw-Tomboulis (CJT) effective action approach a theoretical formalism is established for studying the Bose-Einstein condensation (BEC) in a binary mixture of Bose gases. The effective potential, which preserves the Goldstone theorem, is found in the Hartree-Fock (HF) approximation. This quantity is then used to consider the equation of state (EOS) and the phase transition of the system.

Bose–Einstein condensation in binary mixture of Bose gases

The Bose–Einstein condensation (BEC) in a binary mixture of Bose gases is studied by means of the Cornwall–Jackiw–Tomboulis (CJT) effective action approach. The equations of state (EoS) and various scenarios of phase transitions of the system are considered in detail, in particular, the numerical computations are carried out for symmetry restoration (SR), symmetry nonrestoration (SNR) and inverse symmetry breaking (ISB) for getting an insight into their physical nature. It is shown that due to the cross interaction between distinct components of mixture there occur two interesting phenomena: the high temperature BEC and the inverse BEC, which could be tested in experiments.

The Hydrodynamic Equations of Superfluid Mixtures in Magnetic Traps

The hydrodynamics equations of binary mixtures of Bose gases, Fermi gases, and mixtures of Bose and Fermi gases in the presence of external potentials are derived. These equations can be applied to current experiments on mixtures of atomic gases confined in magnetic traps.

Construction of theory of a binary mixture of nonideal bose gases (or liquids) by the method of collective variables. II. The s-particle density matrices at T=0. Variational calculation of the ground-state energy and density-density correlation functions

The s-particle density matrices at T = O are found by the method of collective variables for a binary mixture of nonideal Bose gases (or liquids). The variational method is used to find the ground-state energy, the excitation spectrum, and the density-density correlation functions. It is shown that the zeroth approximations of the variational and microscopic approaches are consistent. The existence of a Bose condensate in the system is established. A binary mixture of Bose gases with equal masses of the particles is considered as an illustration in the framework of the hard-sphere pseudopotential model.