arXiv subjects

Abdelaali Boudjemaa

Publications and source records attributed to Abdelaali Boudjemaa.

At least 37 records · Page 2Linked to original sources

arXiv2020

Bose-Bose mixtures in a weak-disorder potential: Fluctuations and superfluidity

We study the properties of a homogeneous dilute Bose-Bose gas in a weak-disorder potential at zero temperature. By using the perturbation theory, we calculate the disorder corrections to the condensate density, the equation of state, the compressibility, and the superfluid density as a function of density, strength of disorder, and miscibility parameter. It is found that the disorder potential may lead to modifying the miscibility-immiscibility condition and a full miscible phase turns out to be impossible in the presence of the disorder. We show that the intriguing interplay of the disorder and intra- and interspecies interactions may strongly influence the localization of each component, the quantum fluctuations, and the compressibility, as well as the superfluidity of the system.

cond-mat.dis-nn↗

arXiv2020

Quantum correlations in dipolar droplets: Time-dependent Hartree-Fock-Bogoliubov theory

We investigate the effects of quantum correlations on dipolar quantum droplets. To this end,we derive self-consistent time-dependent Hartree-Fock-Bogoliubov equations that fairly describe the dynamics of the order parameter, the normal, and anomalous quantum correlations of the droplet. We analyze the density profiles, the critical number of particles, the condensate depletion, and the pair correlation function. Our predictions are compared with very recent experimental and Quantum Monte-Carlo simulations results and excellent agreement is found.

cond-mat.quant-gas↗

arXiv2020

Breathing modes of repulsive polarons in Bose-Bose mixtures

We consider impurity atoms embedded in a two-component Bose-Einstein condensate in a quasi-one dimensional regime. We study the effects of repulsive coupling between the impurities and Bose species on the equilibrium of the system for both miscible and immiscible mixtures by numerically solving the underlying coupled Gross-Pitaevskii equations. Our results reveal that the presence of impurities may lead to a miscible-immiscible phase transition due to the interaction of the impurities and the two condensates. Within the realm of the Bogoliubov-de Gennes equations we calculate the quantum fluctuations due to the different types of interactions. The breathing modes and the time evolution of harmonically trapped impurities in both homogeneous and inhomogeneous binary condensates are deeply discussed in the miscible case using variational and numerical means. We show in particular that the self-trapping, the miscibility and the inhomogeneity of the trapped Bose mixture may strongly modify the low-lying excitations and the dynamical properties of impurities. The presence of phonons in the homogeneous Bose mixture gives rise to the damping of breathing oscillations of impurities width.

cond-mat.quant-gas↗

arXiv2020

Singular Soliton Molecules of the Nonlinear Schrodinger Equation

We derive an exact solution to the local nonlinear Schrödinger equation (NLSE) using the Darboux transformation method. The new solution describes the profile and dynamics of a two-soliton molecule. Using an algebraically-decaying seed solution, we obtain a two-soliton solution with diverging peaks, which we denote as singular soliton molecule. We find that the new solution has a finite binding energy. We calculate the force and potential of interaction between the two solitons, which turn out to be of molecular-type. The robustness of the bond between the two solitons is also verified. Furthermore, we obtain a new solution to the nonlocal NLSE using the same method and seed solution. The new solution in this case corresponds to an elastic collision of a soliton, a breather soliton on flat background, and a breather soliton on a background with linear ramp. Finally, we consider an NLSE which is nonlocal in time rather than space. Although we did not find a Lax pair to this equation, we derive three exact solutions.

nlin.PS↗

arXiv2020

Superfluidity and coherence in uniform dipolar binary Bose mixtures

We investigate the superfluidity and the coherence in dipolar binary Bose mixtures using the hydrodynamic approach. Useful analytical formulas for the excitations spectrum, the correlation function, the static structure factor, and the superfluid fraction are derived. We find that in the case of highly imbalanced mixture, the superfluidity can occur in the dilute component only at extremely low temperatures. The behavior of the first-order correlation function for both dipolar and nondipolar Bose mixtures is deeply analyzed. Then we face the two-dimensional case which encodes a non-trivial physics due to the roton modes.

cond-mat.quant-gas↗

arXiv2019

Effects of weak disorder on two-dimensional bilayered dipolar Bose-Einstein condensates

We investigate properties of two-dimensional bilayered dipolar Bose condensed gases in a weak random potential with Gaussian correlation at zero temperature. Here the dipoles are oriented perpendicularly to the layers and in parallel/antiparallel configurations. We calculate analytically and numerically the condensate depletion, the one-body density-matrix, and the superfluid fraction in the framework of the Bogoliubov theory. Our analysis not only provides fascinating new results do not exist in the literature but also shows that the intriguing interplay between the disorder, the interlayer coupling and the polarization orientation may lead to localize/delocalize the condensed particles results in the formation of glassy/superfluid phases. For a pure short-range interaction and a vanishing correlation length and a small interlayer distance, we reproduce the seminal results of Huang and Meng. While for a vanishing interlayer distance, our results reduce to the those obtained for single layer systems.

cond-mat.dis-nn↗

arXiv2019

Two-dimensional quantum droplets in dipolar Bose gases

We calculate analytically the quantum and thermal fluctuations corrections of a dilute quasi-two-dimensional Bose-condensed dipolar gas. We show that these fluctuations may change their character from repulsion to attraction in the density-temperature plane owing to the striking momentum dependence of the dipole-dipole interactions. The dipolar instability is halted by such unconventional beyond mean field corrections leading to the formation of a droplet phase. The equilibrium features and coherence properties exhibited by such droplets are deeply discussed. At finite temperature, we find that the equilibrium density crucially depends on the temperature and on the confinement strength and thus, a stable droplet can exist only at ultralow temperature due to the strong thermal fluctuations.

cond-mat.quant-gas↗

arXiv2019

Effects of quantum fluctuations on the dynamics of dipolar Bose polarons

We study the dynamics of dipolar Bose polarons in the presence of the normal and anomalous fluctuations using the time-dependent Hartree-Fock-Bogoliubov theory. The density profiles of the condensate, the anomalous component and the impurity are deeply analyzed. The time evolution of the width and the center-of-mass oscillation of such quantities is also highlighted. We calculate corrections due to quantum fluctuations and impurity to the chemical potential and the radius of the condensate and of the anomalous component in the weak coupling regime using the Thomas-Fermi approximation. Effects of the dipole-dipole interaction, impurity-host interaction and the anomalous fluctuation on the width and on the breathing frequencies of the impurity are discussed by variational and numerical means.

cond-mat.quant-gas↗

arXiv2019

Dipolar Bose gas with three-body interactions in weak disorder

We study effects of weak disorder with Gaussian correlation function on a dipolar Bose gas with three-body interactions using the Hartree-Fock-Bogoliubov theory. Corrections due to quantum, thermal and disorder fluctuations to the condensate depletion, the one-body density correlation function as well as to the equation of state and the ground state energy are properly calculated. We show that the intriguing interplay of the disorder, dipole-dipole interactions and three-body interactions plays a fundamental role in the physics of the system. Interestingly, we find that the three-body interactions release atoms localized in the respective minima of the random potential.

cond-mat.dis-nn↗

arXiv2019

Interwires polar soliton molecules in a biwire system

We investigate stability the dynamical properties of one-dimensional interwires polar soliton molecules in a biwire setup with dipole moments aligned perpendicularly to the line of motion and in opposite directions in different wires. Numercial results based on a nonlocal nonlinear Schrödinger equation reveal the existence of a bound state leading to the formation of a molecule. We show that the degree of the nonlocality and the interwire separation play an important role in stabilizing the molecules. Dynamics of the width and center-of-mass of a solitons is also analyzed in terms of the system parameters.

nlin.PS↗

arXiv2018

Effects of the Lee-Huang-Yang quantum corrections on a disordered dipolar Bose gas

We study the behavior of a quantum dipolar Bose condensate with the Lee-Huang-Yang quantum corrections at zero temperature in the presence of weak disorder potential. We solve the underlying nonlocal Gross-Pitaevskii equation using a perturbative theory. The role of both the Lee-Huang-Yang term and the disorder potential on the condensed fraction, the equation of state, the compressibility and the superfluid density is deeply analyzed. Surprisingly, we find that the Lee-Huang-Yang quantum corrections not only arrest the dipolar implosion but also lead to reduce the condensate fluctuations due to the disorder effects prohibiting the formation of a Bose glass state. We show that the superfluid density exhibits unconventional behavior.

cond-mat.dis-nn↗

arXiv2018

Fluctuations and quantum self-bound droplets in a dipolar Bose-Bose mixture

We systematically investigate the properties of three-dimensional dipolar binary Bose mixture at low temperatures. A set of coupled self-consistent equations of motion are derived for the two condensates. In the homogeneous case, useful analytical formulas for the condensate depletion, the anomalous density, the ground-state energy, and the equation of state are obtained. The theory is extended to the inhomogeneous case and the importance of the inhomogeneity is highlighted. Our results open up a new avenue for studying dipolar mixture droplets. Impacts of the dipole-dipole interaction on the stability, density profiles, and the size of the self-bound droplet are deeply discussed. The finite-temperature behavior of such a state is also examined.

cond-mat.quant-gas↗

arXiv2018

Quantum and thermal fluctuations in two-component Bose gases

We study the effects of quantum and thermal fluctuations on Bose-Bose mixtures at finite temperature employing the time-dependent Hartree-Fock-Bogoliubov (TDHFB) theory. The theory governs selfconsistently the motion of the condensates, the noncondensates and of the anomalous components on an equal footing. The finite temperature criterion for the phase separation is established. We numerically analyze the temperature dependence of different densities for both miscible and immiscible mixtures. We show that the degree of the overlap between the two condensates and the thermal clouds is lowered and the relative motion of the centers-of-mass of the condensed and thermal components is strongly damped due to the presence of the pair anomalous fluctuations. Our results are compared with previous theoretical and experimental findings. On the other hand, starting from our TDHFB equations, we develop a random-phase theory for the elementary excitations in a homogeneous mixture. We find that the normal and anomalous fluctuations may lead to enhance the excitations and the thermodynamics of the system.

cond-mat.quant-gas↗

arXiv2017

Collective excitations of a dilute Bose gas at finite temperature: TDHFB Theory

Using the time-dependent Hartree-Fock-Bogoliubov approach, where the condensate is coupled with the thermal cloud and the anomalous density, we study the equilibrium and the dynamical properties of three-dimensional quantum-degenerate Bose gas at finite temperature. Effects of the anomalous correlations on the condensed fraction and the critical temperature are discussed. In uniform Bose gas, useful expressions for the Bogoliubov excitations spectrum, the first and second sound, the condensate depletion and the superfluid fraction are derived. Our results are tested by comparing the findings computed by Quantum Monte Carlo simulations. We present also a systematic investigation of the collective modes of a Bose condensate confined in an external trap. Our predictions are in qualitative agreement with previous experimental and theoretical results. We show in particular that our theory is capable of explaining the so-called anomalous behavior of the m=0 mode.

cond-mat.quant-gas↗

arXiv2017

Quantum gas of polar molecules ensembles at ultralow temperatures: f-wave superfluids

We investigate novel f-wave superfluids of fermionic polar molecules in a two-dimensional bilayer system with dipole moments polarized perpendicular to the layers and in opposite directions in different layers. The solution of the BCS gap equation reveals that these unconventional superfluids emerge at temperatures on the level of femtokelvin which opens up new possibilities to explore the topological f+i f phase, quantum interferometry and Majorana fermions in experiments with ultracold polar molecules. The experimental realization of such interesting novel f-wave pairings is discussed.

cond-mat.quant-gas↗

arXiv2017

Quantum dilute droplets of dipolar bosons at finite temperature

We systematically study the properties of dipolar Bose gases with two- and three-body contact interactions at finite temperature using the Hartree-Fock-Bogoliubov-Popov approximation. In uniform case, we obtain an exciting new extension of the seminal Lee-Huang-Yang corrected equation of state that depends explicitly on the thermal fluctuations and on the coupling constant of the three-body interaction. We investigate, on the other hand, the effects of thermal fluctuations on the occurrence and stability of a droplet state in a Bose-Einstein condensate with strong dipole-dipole interactions. We find that at finite temperature, the droplet phase appears as a narrow peak surrounded by a broader thermal halo. We show that the number of particles inside the droplet decays with increasing temperature.

cond-mat.quant-gas↗

arXiv2017

Dipolar Bose gas with three-body interactions at finite temperature

We investigate effects of three-body contact interactions on a trapped dipolar Bose gas at finite temperature using the Hartree-Fock-Bogoliubov approximation. We analyze numerically the behavior of the transition temperature and the condensed fraction. Effects of the three-body interactions, anomalous pair correlations and temperature on the collective modes are discussed.

cond-mat.quant-gas↗

arXiv2016

Unconventional superfluids of fermionic polar molecules in a bilayer system

We study unconventional superfluids of fermionic polar molecules in a two-dimensional bilayer system with dipoles are head-to-tail across the layers. We analyze the critical temperature of several unconventional pairings as a function of different system parameters. The peculiar competition between the $d$- and the $s$- wave pairings is discussed. We show that the experimental observation of such unconventional superfluids requires ulralow temperatures, which opens up new possibilities to realize several topological phases.

cond-mat.quant-gas↗