Self-localized state and solitons in a Bose-Einstein-condensate–impurity mixture at finite temperature

2016

Phys. Rev. A

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We study the collective modes of a one-dimensional (1D) harmonically trapped Bose-Einstein condensate (BEC) in the presence of the anomalous density using the time-dependent-Hartree-FockBogoliubov (TDHFB) theory. Within the hydrodynamic equations, we derive analytical expressions for the mode frequencies and the density fluctuations of the anomalous density which constitutes the minority component at very low temperature and feels an effective external potential exerted by the majority component i.e. the condensate. On the other hand, we numerically examine the temperature dependence of the breathing mode oscillations of the condensate at finite temperature in the weak-coupling regime. At zero temperature, we compare our predictions with available experimental data, theoretical treatments and Monte carlo simulations in all interaction regimes and the remaining hindrances are emphasized. We show that the anomalous correlations have a non-negligible role on the collective modes at both zero and finite temperatures.

Section: A Analytical Resultsmentioning

confidence: 99%

“…The aim of the present work is to investigate the collective modes of both the condensate and the anomalous components in a quasi-1D trapped Bose gas at finite temperature utilizing our TDHFB theory [21,23,29,30,[34][35][36][37][38]. The TDHFB is a self-consistent approach describing the dynamics of ultracold Bose gases.…”

Section: Introductionmentioning

confidence: 99%

Collective modes of a one-dimensional trapped Bose gas in the presence of the anomalous density

2016

Phys. Rev. A

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“…An important feature of these * a.boudjemaa@univ-chlef.dz mixtures is that when neutral impurity atoms immersed in a BEC can spontaneously form a self-localize state. This localized state, within the strong coupling approach, exhibits a solitonic behavior at both zero and finite temperatures [17,26] in quasi-1D geometry. These solitons are reminiscent of the well known optical wave solitons [28].…”

Section: Introductionmentioning

confidence: 95%

“…We neglect the mutual interactions of impurity atoms since we assume that their number and local density remains sufficiently small [15,16] and hence there is no impurity fluctuation. The TDHFB equations which govern the dynamics of the condensate, the thermal cloud, the anomalous density and the impurity read [26,27] …”

Section: Formalismmentioning

confidence: 99%

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Spontaneous formation of bright solitons in self-localized impurities in Bose–Einstein condensates

Communications in Nonlinear Science and Numerical Simulation

2016

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We study the formation of bright solitons in the impurity component of Bose-Einstein condensateimpurity mixture by using the time-dependent Hartree-Fock-Bogoliubov theory. While we assume the boson-boson and impurity-boson interactions to be effectively repulsive, their character can be changed spontaneously from repulsive to attractive in the presence of strong anomalous correlations. In such a regime the impurity component becomes a system of effectively attractive atoms leading automatically to the generation of bright solitons. We find that this soliton decays at higher temperatures due to the dissipation induced by the impurity-host and host-host interactions. We show that after a sudden increase of the impurity-boson strength a train of bright solitons is produced and this can be interpreted in terms of the modulational instability of the time-dependent impurity wave function.

Superfluidity and Bose–Einstein Condensation in a Dipolar Bose Gas with Weak Disorder

2015

J Low Temp Phys

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We investigate the properties of a three-dimensional homogeneous dipolar Bose gas in a weak random potential with a Gaussian correlation function at finite temperature. Using the Bogoliubov theory (beyond the mean field), we calculate the superfluid and the condensate fractions in terms of the interaction strength on the one hand and in terms of the width and the strength of the disorder on the other. The influence of the disordered potential on the second-order correlation function, the ground state energy, and the chemical potential is also analyzed. We find that for fixed strength and correlation length of the disorder potential, the dipole-dipole interaction leads to modify both the condensate and the superfluid fractions. We show that for a strong disorder strength the condensed fraction becomes larger than the superfluid fraction. We discuss the effect of the trapping potential on a disordered dipolar Bose in the regime of large number of particles.