Entanglement Properties in Two-Component Bose-Einstein Condensate

We investigate entanglement inseparability and bipartite entanglement of in two-component Bose-Einstein condensate in the presence of the nonlinear interatomic interaction, interspecies interaction. Entanglement inseparability and bipartite entanglement have the similar properties. More entanglement can be generated by adjusting the nonlinear interatomic interaction and control the time interval of the entanglement by adjusting interspecies interaction.     

Single-Particle Coherence and RMQFI in Two-Species BECs

We investigate the relation between the single-particle coherence and the reciprocal of the mean quantum Fisher information per particle (RMQFI) in Bose-Einstein condensates (BECs) in the presence of interatomic interaction and interspecies interaction. The single-particle coherence and RMQFI depend on the interatomic interaction. It is shown that the larger interatomic interaction more rapidly induces entanglement.     

驱动场作用下二分量BEC中原子数密度的演化

运用数值模拟研究了二分量玻色-爱因斯坦凝聚体(BEC)原子数密度的动力学行为,讨论了驱动场耦合强度、不同分量间原子作用强度、射频场频率及同分量内原子作用强度对二分量原子数密度演化特性的影响.结果显示:原子数密度随时间近似作周期性振荡,其振荡的周期随驱动耦合场强度、不同分量原子间作用强度的增大而减小,随自耦合强度的增大而增大;射频场频率的变化并不显著改变原子数密度振荡的周期,但它的增大会和自耦合强度的增大一样导致原子密度振荡的振幅减小.     

Sudden onset of log-periodicity and superdiffusion in non-Markovian random walks with amnestically induced persistence: exact results

We consider strongly interacting boson-boson mixtures on one-dimensional lattices and, by adopting a qualitative mean-field approach, investigate their quantum phases as the interspecies repulsion is increased. In particular, we analyze the low-energy quantum emulsion metastable states occurring at large values of the interspecies interaction, which are expected to prevent the system from reaching its true ground state. We argue a significant decrease in the visibility of the time-of-flight images in the case of these spontaneously disordered states.     

Interspecies stress in momentum equations for dense binary particulate systems

For two-species particulate systems, ensemble averaged continuity and momentum equations for each species are derived based on the Liouville equation of the system. The ensemble average used is species specific. It is found that the interaction between species results in not only the interspecies force but also a stress in the momentum equations. In the limit that particles of one of the species can be considered as a continuum, the existence of the interspecies stress enables us to reduce the derived equations to the familiar form for dispersed two-phase flows.     

Phase of Two-Component Bose-Einstein Condensates with a Coupling Drive

By using the invariant theory, we study the phases of two-component Bose-Einstein condensates with a coupling drive under the case that the strength of the interatomic interaction in each condensate equals the interspecies interaction. The dynamical and geometric phases are presented respectively. The Aharonov-Anandan phase is also obtained under the cyclical evolution.     

Bright solitons and soliton trains in a fermion-fermion mixture

We use a time-dependent dynamical mean-field-hydrodynamic model to predict and study bright solitons in a degenerate fermion-fermion mixture in a quasi-one-dimensional cigar-shaped geometry using variational and numerical methods. Due to a strong Pauli-blocking repulsion among identical spin-polarized fermions at short distances there cannot be bright solitons for repulsive interspecies fermion-fermion interactions. However, stable bright solitons can be formed for a sufficiently attractive interspecies interaction. We perform a numerical stability analysis of these solitons and also demonstrate the formation of soliton trains. These fermionic solitons can be formed and studied in laboratory with present technology.     

Atomic Tunnelling Dynamics of Two Squeezed Bose-Einstein Condensates

In this paper, tunnelling dynamics of squeezed Bose-Einstein condensates (BEC's) in the presence of the nonlinear self-interaction of each species, the interspecies nonlinear interaction, and the Josephson-like tunnelling interaction is investigated by using the second quantization approach. The influence of BEC squeezing on macroscopic quantum self-trapping (MQST) and quantum coherent atomic tunnelling is analyzed in detail. It is shown that the MQST and coherent atomic tunnelling between two squeezed BEC's can be manipulated through changing squeezing amplitude and squeezing phase of BEC squeezed states.     

Landau-Zener tunneling of Bose-Fermi mixture in double-well

The nonlinear Landau-Zener tunneling of a Bose-Fermi mixture in a double-well potential is studied in the present paper. The effect of interaction parameters on bosonic and fermionic tunneling probability is studied for the mixture of ⁴⁰K-⁸⁷Rb. The tunneling phenomena of the system can be controled by adjusting sweeping rate, intraspecies interaction, interspecies interaction and the numbers of bosons and fermions. It is noted that there are three different regions in phase diagram: self-trapping (ST), complete tunneling (CT) and incomplete tunneling (ICT).     

Effect of interactions on harmonically confined Bose-Fermi mixtures in optical lattices

We investigate a Bose-Fermi mixture in a three-dimensional optical lattice, trapped in a harmonic potential. Using generalized dynamical mean-field theory, which treats the Bose-Bose and Bose-Fermi interaction in a fully nonperturbative way, we show that for experimentally relevant parameters a peak in the condensate fraction close to the point of vanishing Bose-Fermi interaction is reproduced within a single-band framework. We identify two physical mechanisms contributing to this effect: the spatial redistribution of particles when the interspecies interaction is changed and the reduced phase space for strong interactions, which results in a higher temperature at fixed entropy.     

Tunneling Dynamics of Two-Species Bose-Einstein Condensates

We have studied the tunneling dynamics of two-species Bose-Einstein condensates. It is shown that the population difference and the Josephson-like tunneling current between the two condensates exhibit oscillation behaviors and there exists macroscopic quantum self-trapping, which strongly depends on the initial state, interatomic nonlinear self-interaction, interspecies nonlinear interaction, and the total number of atoms in the two condensates.     

A Dynamical Phase Transition of Binary Species BECs Mixtures in a Double Well Potential

We investigate the critical behavior in tunneling dynamics of a binary mixture of Bose-Einstein condensates (BECs) trapped in a symmetric double well potential. By gradually increasing the interspecies interaction, we characterize a continuous dynamical phase transition behavior which involves power law scaling. This dynamical phase transition is a consequence of separatrix crossing as we revealed by poincaré section analysis.     

Quantum Statistical Properties in Two—Species Bose—Einstein Condensates

We have studied quantum statistical properties in a zero-temperature two-species Bose-Einstein condensate system in the presence of the nonlinear self-interaction of each species,the interspecies nonlinear interaction,and the Jisephson-like tunneling interaction.It is found that the two condensates may periodically exhibit sub-Poissonian distribution.It is revealed that the correlation between the two condensates can be nonclassical,which means that there exists a violation of Cauchy-Schwartz inequality.The nonclassical effect about the correlation between the two condensates can be realized experimentally by properly preparing the total number of atoms in the two condensates.     

Splitting dynamics of a two-species Bose-Einstein condensate in two translating traps

We extend our previous work of splitting a single-species Bose-Einstein condensate in two translating traps to a two-species condensate. Different from the single species case where interaction is considered as a damping mechanism to the motion of the condensate, we find that, in the two species case, the damping effect is much less obvious and the splitting dynamics exhibit different behaviors. The distribution of each component are not damped towards 50:50 for large interaction strength in the two wells. Our conclusions are supported by investigating the dependence of the splitting on both the translation speed and the interspecies scattering length.     

Fermi-Bose quantum degenerate 40K-87Rb mixture with attractive interaction

We report on the achievement of simultaneous quantum degeneracy in a mixed gas of fermionic 40K and bosonic 87Rb. Potassium is cooled to 0.3 times the Fermi temperature by means of an efficient thermalization with evaporatively cooled rubidium. Direct measurement of the collisional cross-section confirms a large interspecies attraction. This interaction is shown to affect the expansion of the Bose-Einstein condensate released from the magnetic trap, where it is immersed in the Fermi sea.     

Exact Temporal Evolution of Two-Species Bose-Einstein Condensates

We construct exact stationary solutions to the one-dimensional coupled Gross-Pitaevskii equations for the two-species Bose-Einstein condensates with equal intraspecies and interspecies interaction constants. Three types of complex solutions as well as their soliton limits are derived. By making use of the SU(2) unitary symmetry, we further obtain analytical time-evolving solutions. These solutions exhibit spatiotemporal periodicity.     

Equation of state of a Fermi gas in the BEC-BCS crossover: a quantum Monte Carlo study

We calculate the equation of state of a two-component Fermi gas with attractive short-range interspecies interactions using the fixed-node diffusion Monte Carlo method. The interaction strength is varied over a wide range by tuning the value a of the s-wave scattering length of the two-body potential. For a>0 and a smaller than the inverse Fermi wave vector our results show a molecular regime with repulsive interactions well described by the dimer-dimer scattering length a(m)=0.6a. The pair correlation functions of parallel and opposite spins are also discussed as a function of the interaction strength.     

异核两组分玻色-爱因斯坦凝聚体中暗孤子的形成及其性质

数值模拟准一维异核两组分玻色-爱因斯坦凝聚体在谐振子势阱中的运动,研究调制不稳定性条件(MI条件)下暗孤子的形成及其性质.在调制不稳定性条件下,凝聚体基态形成后,瞬间使组分间的相互排斥力变为相互吸引力,实时演化可以形成暗孤子.对各组分自身相互作用系数分析发现,它们之间满足一定关系时暗孤子在不同的组分内形成,而且形成的暗孤子在谐振子势阱中呈现周期性的往返对穿运动.讨论了形成暗孤子数目与两种粒子的质量比率和粒子数比率存在的关系.     

驱动场作用下二分量BEC原子数密度演化中的崩塌与复苏现象

本文运用数值模拟研究了二分量BEC原子数密度的长时间动力学行为,讨论了驱动场Rabi频率、二分量初始相对相位差、驱动场耦合强度、同分量内原子作用强度及不同分量间原子作用强度对阱中原子数密度演化特性的影响.结果表明:长时间内阱中原子数密度的演化出现与短时间内周期性余弦振荡不同的新现象,即呈现典型的量子崩塌与复苏.     

Formation of combined solitons in two-component Bose—Einstein condensates

<正>We investigate the combined soliton solutions of two-component Bose—Einstein condensates with external potential. The "phase diagram" is obtained for the formation regions of different combined solitons.Our results show that the intraspecies(interspecies) interaction strengths and the external trapped potential clearly affect the formation of dark-dark, bright-bright,and dark-bright soliton solutions in different regions.Especially,we find that the bright-bright (dark-dark) soliton can exist in the case of both repulsive(attractive) intraspecies interaction strengths in the presence of external potential.This novel phenomenon is completely different from the formation of soliton solution of one-component Bose-Einstein condensates without external potential,and it will be useful for the study of two-component Bose-Einstein condensates.