Using mean-field theory, we study the equilibrium properties of boson-fermion mixtures confined in a harmonic pancake-shaped trap at zero temperature. When the modulus of the $s$-wave scattering lengths are comparable to the mixture thickness, two-dimensional scattering events introduce a logarithmic …

[Phys. Rev. A 79, 063632] Published Tue Jun 30, 2009

Using a Luttinger-liquid approach we study the quantum fluctuations of a Bose-Josephson junction, consisting of a Bose gas confined to a quasi-one-dimensional ring trap which contains a localized repulsive potential barrier. For an infinite barrier we study the one-particle and two-particle static c…

[Phys. Rev. A 79, 063633] Published Tue Jun 30, 2009

We consider a periodic lattice loaded with pairs of bosonic atoms tightly bound to each other via strong attractive on-site interaction that exceeds the intersite tunneling rate. An ensemble of such lattice dimers is accurately described by an effective Hamiltonian of hard-core bosons with strong ne…

[Phys. Rev. A 79, 063634] Published Tue Jun 30, 2009

We describe an apparatus for quickly and simply producing ${}^{87}\text{R}\text{b}$ Bose-Einstein condensates. It is based on a magnetic quadrupole trap and a red-detuned optical dipole trap. We collect atoms in a magneto-optical trap (MOT) and then capture the atoms in a magnetic quadrupole trap and force rf evaporatio…

[Phys. Rev. A 79, 063631] Published Mon Jun 29, 2009

In this work, we examine a system for coherent transfer of atoms into a Bose-Einstein condensate. We utilize two spatially separate Bose-Einstein condensates in different hyperfine ground states held in the same dc magnetic trap. By means of a pulsed transfer of atoms, we are able to show a clear re…

[Phys. Rev. A 79, 063630] Published Thu Jun 25, 2009

We consider an ultracold rotating Bose gas in a harmonic trap close to the critical angular velocity, so that the system can be considered to be confined to the lowest Landau level. With this assumption we prove that the Gross-Pitaevskii energy functional accurately describes the ground-state energy…

[Phys. Rev. A 79, 063626] Published Wed Jun 24, 2009

In this paper, we investigate the ground-state properties of a bosonic Tonks-Girardeau (TG) gas confined in a one-dimensional periodic potential. The single-particle reduced density matrix is computed numerically for systems up to $N=265$ bosons. Scaling analysis of the occupation number of the lowest…

[Phys. Rev. A 79, 063627] Published Wed Jun 24, 2009

We present a series of theoretical studies of the boundary between a superfluid and a normal region in a partially polarized gas of strongly interacting fermions. We present mean-field estimates of the surface energy in this boundary as a function of temperature and scattering length. We discuss the…

[Phys. Rev. A 79, 063628] Published Wed Jun 24, 2009

We discuss the ground state of the two-dimensional Bose-Hubbard (BH) Hamiltonian, relevant for rotating gaseous Bose-Einstein condensates, by employing U(1) quantum rotor approach and the topologically constrained path integral that includes a summation over U(1) topological charge. We derive an eff…

[Phys. Rev. A 79, 063629] Published Wed Jun 24, 2009

We quantify the effect of phase fluctuations on atom chip interferometry of Bose-Einstein condensates. At very low temperatures, we observe small phase fluctuations, created by mean-field depletion, and a resonant production of vortices when the two clouds are initially in antiphase. At higher tempe…

[Phys. Rev. A 79, 063624] Published Tue Jun 23, 2009

We present a theoretical study of vortices within a harmonically trapped Bose-Einstein condensate in a rotating optical lattice. Due to the competition between vortex-vortex interactions and pinning to the optical lattice, we find a very complicated energy landscape, which leads to hysteretic evolut…

[Phys. Rev. A 79, 063625] Published Tue Jun 23, 2009

We compute the coefficients of bulk viscosity for a nonrelativistic superfluid corresponding to a fermionic system close to the unitarity limit. We consider the low temperature regime assuming that the transport properties of the system are dominated by phonons. To compute the coefficients of bulk v…

[Phys. Rev. A 79, 063623] Published Mon Jun 22, 2009

We study polarization effects of two-component atomic Fermi gases loaded on three-leg triangular optical lattice by using the density-matrix renormalization-group method. Concentrating on a case in which a Mott phase coexists with metallic ones, we observe plateulike structures in the Mott phase pol…

[Phys. Rev. A 79, 061602(R)] Published Fri Jun 19, 2009

We show that thermalization and the breakdown of integrability in the one-dimensional Lieb-Liniger model caused by local three-body elastic interactions is suppressed by pairwise quantum correlations when approaching the strongly correlated regime. If the relative momentum $k$ is small compared to the…

[Phys. Rev. A 79, 061603(R)] Published Fri Jun 19, 2009

We analytically derive the general pseudopotential operator of an arbitrary isotropic interaction for particles confined in two-dimensional (2D) systems using the frame work developed by Huang and Yang for three-dimensional scattering. We also analytically derive the low-energy dependence of the sca…

[Phys. Rev. A 79, 065603] Published Fri Jun 19, 2009

We derive closed analytical expressions for the order parameter $\Phi \left(x\right)$ and for the chemical potential $\mu$ of a Bose-Einstein condensate loaded into a harmonically confined, one-dimensional optical lattice for sufficiently weak, repulsive, or attractive interaction and not too strong laser intensities. O…

[Phys. Rev. A 79, 063621] Published Thu Jun 18, 2009

We present full three-dimensional numerical calculations of single vortex states in rotating dipolar condensates. We consider a Bose-Einstein condensate of ${}^{52}\text{C}\text{r}$ atoms with dipole-dipole and $s$-wave contact interactions confined in an axially symmetric harmonic trap. We obtain the vortex states by num…

[Phys. Rev. A 79, 063622] Published Thu Jun 18, 2009

We study the tunneling of Bogoliubov excitations through a barrier in a Bose-Einstein condensate. We extend our previous work [S. Tsuchiya and Y. Ohashi, Phys. Rev. A 78, 013628 (2008)] to the case when condensate densities are different between the left and right of the barrier potential. In the fr…

[Phys. Rev. A 79, 063619] Published Wed Jun 17, 2009

Half-integer-photon resonances in a periodically shaken double well are investigated on the level of the $N$-particle quantum dynamics. Contrary to nonlinear mean-field equations, the linear $N$-particle Schrödinger equation does not contain any nonlinearity which could be the origin of such resonances.…

[Phys. Rev. A 79, 063620] Published Wed Jun 17, 2009

We generalize the concept of quantum phase transitions, which is conventionally defined for a ground state and usually applied in the thermodynamic limit, to one for metastable states in finite-size systems. In particular, we treat the one-dimensional Bose gas on a ring in the presence of both inter…

[Phys. Rev. A 79, 063616] Published Wed Jun 10, 2009

Anderson localization of matter waves was recently observed with cold atoms in a weak one-dimensional disorder realized with laser speckle potential [Billy et al., Nature (London) 453, 891 (2008)]. The latter is special in that it does not have spatial frequency components above certain cutoff $q_c$. …

[Phys. Rev. A 79, 063617] Published Wed Jun 10, 2009

We investigate the rotational properties of a Bose-Einstein condensate (BEC) in an effective magnetic field. The corresponding gauge potential is optically generated, and based on the adiabatic motion of the atoms. We demonstrate that the nucleation of vortices is seeded by instabilities in surface …

[Phys. Rev. A 79, 063618] Published Wed Jun 10, 2009

We consider an atomic Fermi gas confined in a uniform optical lattice potential, where the atoms can pair into molecules via a magnetic field controlled narrow Feshbach resonance. Thus by adjusting the magnetic field the portion of fermionic and bosonic particles in the system can be continuously va…

[Phys. Rev. A 79, 063615] Published Mon Jun 08, 2009

Antiferromagnetic, Mott-insulator, $d$-wave, and gossamer superfluid phases are calculated for two-dimensional (2D) square lattices from the extended Hubbard $\left(t\text{−}J\text{−}U\right)$ model using the Gutzwiller projection method and renormalized mean-field theory. The phase separation between antiferromagnetic and $d$-wa…

[Phys. Rev. A 79, 063611] Published Fri Jun 05, 2009

We investigate the dynamics of a Bose-Einstein condensate held in an optical lattice under the influence of a strong periodic driving potential. Studying the mean-field version of the Bose-Hubbard model reveals that the condensate becomes dynamically unstable when the effective intersite tunneling b…

[Phys. Rev. A 79, 063612] Published Fri Jun 05, 2009

A technique is described by which light-induced gauge potentials allow systems of ultracold neutral atoms to behave like charged particles in a magnetic field. Here, atoms move in a uniform laser field with a spatially varying Zeeman shift and experience an effective magnetic field. This technique i…

[Phys. Rev. A 79, 063613] Published Fri Jun 05, 2009

We consider an electron interacting with a Bose-Einstein condensate of atoms that can form negative ions. The binding energy $E_a$ of an electron by a single neutral atom gives rise to a continuous band of electronic quantum states resulting from the process of charge exchange among the condensate atom…

[Phys. Rev. A 79, 063614] Published Fri Jun 05, 2009

We examine structural and dynamical properties of quantum resonances associated with an avoided crossing and identify the parameter shifts where these properties attain extreme values. Thus the concept of avoided crossing resonance can be defined in different ways, which do not coincide in the gener…

[Phys. Rev. A 79, 065602] Published Fri Jun 05, 2009

We calculate the critical temperature for Bose-Einstein condensation in a gas of bosonic atoms across a Feshbach resonance and show how medium effects at negative scattering lengths give rise to pairs reminiscent of the ones responsible for fermionic superfluidity. We find that the formation of pair…

[Phys. Rev. A 79, 063609] Published Thu Jun 04, 2009

We investigate a model of a two-component Bose-Einstein condensate residing in an optical lattice. Within a Bogoliubov approach at the mean-field level, we derive exact analytical expressions for the excitation spectrum of the two-component condensate when taking into account hopping and interaction…

[Phys. Rev. A 79, 063610] Published Thu Jun 04, 2009

We propose an experimental procedure to cool fermionic atoms loaded into an optical lattice. The central idea is to spatially divide the system into entropy-rich and -poor regions by shaping the confining potential profile. Atoms in regions of high entropy per particle are subsequently isolated from…

[Phys. Rev. A 79, 061601(R)] Published Wed Jun 03, 2009

We theoretically study the influence of weak interactions on the diffusive expansion of a Bose-Einstein condensate in a three-dimensional random potential. For this purpose we develop a perturbative approach and calculate analytically the first-order nonlinear correction to the ensemble-averaged ato…

[Phys. Rev. A 79, 063604] Published Wed Jun 03, 2009

We measure the temperature of ultracold ${}^{87}\text{R}\text{b}$ gases transferred into an optical lattice and compare to noninteracting thermodynamics for a combined lattice-parabolic potential. Absolute temperature is determined at low temperature by fitting quasimomentum distributions obtained using band mapping, i.…

[Phys. Rev. A 79, 063605] Published Wed Jun 03, 2009

We study the critical velocity of a Bose-condensed gas in a moving one-dimensional optical lattice potential at finite temperatures. Solving the Gross-Pitaevskii equation and the Bogoliubov equations, within the Popov approximation, we calculate the Bogoliubov excitations with varying lattice veloci…

[Phys. Rev. A 79, 063606] Published Wed Jun 03, 2009

We explore in this paper a harmonically trapped asymmetric fermionic superfluid in a two-dimensional optical lattice with pairing interactions between the neighboring sites, by self-consistently solving Bogliubov–de Gennes equations. We find the superfluid generally phase separates into a $d$-wave pai…

[Phys. Rev. A 79, 063607] Published Wed Jun 03, 2009

The problem of the transcritical flow of a Bose-Einstein condensate through a wide repulsive penetrable barrier is studied analytically using the combination of the locally steady “hydraulic” solution of the one-dimensional Gross-Pitaevskii equation and the solutions of the Whitham modulation equati…

[Phys. Rev. A 79, 063608] Published Wed Jun 03, 2009

We study the dynamics of a trapped spin-1 condensate in a magnetic field. First, we analyze the homogeneous system, for which the dynamics can be understood in terms of orbits in phase space. We analytically solve for the dynamical evolution of the populations of the various Zeeman components of the…

[Phys. Rev. A 79, 063603] Published Tue Jun 02, 2009

We apply a kinetic model to predict the existence of an instability mechanism in elongated Bose-Einstein condensates. Our kinetic description, based on the Wigner formalism, is employed to highlight the existence of unstable Bogoliubov waves that may be excited in the counterpropagation configuratio…

[Phys. Rev. A 79, 065601] Published Tue Jun 02, 2009

Bosonic Josephson junctions can be realized by confining ultracold gases of bosons in multiwell traps and studied theoretically with the $M$-site Bose-Hubbard model. We show that canonical equilibrium states of the $M$-site Bose-Hubbard model may be approximated by mixtures of coherent states, provided …

[Phys. Rev. A 79, 063601] Published Mon Jun 01, 2009

We discuss the thermodynamics of a nonrelativistic gas of bosons with a local repulsive interaction. In particular, we compute the temperature and density dependences of pressure, energy and entropy densities, superfluid and condensate fractions, correlation length, specific heat, isothermal and adi…

[Phys. Rev. A 79, 063602] Published Mon Jun 01, 2009

We present a simple derivation of the energy formula found by Tan, relative to the single-channel Hamiltonian relevant for ultracold Fermi gases. This derivation is generalized to particles with different masses, to arbitrary mixtures, and to two-dimensional space. We show how in a field-theoretic a…

[Phys. Rev. A 79, 053640] Published Fri May 29, 2009

The lifetime of ${}^{87}\text{R}\text{b}$ atoms trapped in a $\mathsf{z}$ wire trap generated by a closed-circuit superconductive current on a ${\text{MgB}}_2$ strip is measured as a function of the distance between the atom and the strip. The lifetime is found to be longer than 10 s at a distance of $40\mu \text{m}$. This value is an order of magnitude…

[Phys. Rev. A 79, 053641] Published Fri May 29, 2009

We propose the subwavelength localization via adiabatic passage (SLAP) technique to coherently achieve state-selective patterning of matter waves well beyond the diffraction limit. The SLAP technique consists in coupling two partially overlapping and spatially structured laser fields to three intern…

[Phys. Rev. A 79, 053638] Published Thu May 28, 2009

We propose the realization of topological quantum states in a cold-atom system, using a two-dimensional hexagonal optical lattice and a light-induced periodic vector potential. A necessary condition for observing the topological states is the realization of a confining potential with a flat bottom a…

[Phys. Rev. A 79, 053639] Published Thu May 28, 2009

We discuss the Aharonov-Bohm effect of a magnetic flux for its influence on a two-dimensional quantum cloak. It is shown that the matter wave of a charged particle under the global influence of the Aharonov-Bohm effect can still be perfectly cloaked and guided by the quantum cloak. Since the presenc…

[Phys. Rev. A 79, 051605(R)] Published Wed May 27, 2009

The Berezinskii-Kosterlitz-Thouless (BKT) mechanism describes the breakdown of superfluidity in a two-dimensional Bose gas or a two-dimensional gas of paired fermions. In the latter case, a population imbalance between the two pairing partners in the Fermi mixture is known to influence pairing chara…

[Phys. Rev. A 79, 053637] Published Wed May 27, 2009

A Bose gas with repulsive interactions in a generic power-law potential is studied in the Hartree-Fock approximation. The scaling parameter characterizing the role of two-body repulsive interactions is expressed in terms of the scaled scattering length and the trap parameter. The chemical potential …

[Phys. Rev. A 79, 055603] Published Wed May 27, 2009

We study the effect of the induced interaction on the superfluid transition temperature of a Fermi gas with a Bose-Einstein condensation–Bardeen-Cooper-Schrieffer (BEC-BCS) crossover. The Gorkov-Melik-Barkhudarov theory about the induced interaction is extended from the BCS side to the entire crosso…

[Phys. Rev. A 79, 053636] Published Fri May 22, 2009

We develop a strong-coupling perturbation theory for the extended Bose-Hubbard model with on-site and nearest-neighbor boson-boson repulsions on $\left(d>1\right)$-dimensional hypercubic lattices. Analytical expressions for the ground-state phase boundaries between the incompressible (Mott or charge-density-w…

[Phys. Rev. A 79, 053634] Published Thu May 21, 2009

Perfect single-crystal neutron interferometers are adversely sensitive to environmental disturbances, particularly mechanical vibrations. The sensitivity to vibrations results from the slow velocity of thermal neutrons and the long measurement time that are encountered in a typical experiment. Conse…

[Phys. Rev. A 79, 053635] Published Thu May 21, 2009

A strong-coupling expansion for the Green’s functions, self-energies, and correlation functions of the Bose-Hubbard model is developed. We illustrate the general formalism, which includes all possible (normal-phase) inhomogeneous effects in the formalism, such as disorder or a trap potential, as wel…

[Phys. Rev. A 79, 053631] Published Wed May 20, 2009

We describe a pairing mean-field theory related to the Hartree-Fock-Bogoliubov approach, and apply it to the dynamics of dissociation of a molecular Bose-Einstein condensate into correlated bosonic atom pairs. We also perform the same simulation using two stochastic phase-space techniques for quantu…

[Phys. Rev. A 79, 053632] Published Wed May 20, 2009

We use functional-integral methods for an estimate of the three-body loss in a three-component ${}^6\text{L}\text{i}$ ultracold atom gas. We advocate a simple picture where the loss proceeds by the formation of a three-atom bound trimer state, the trion. In turn, the effective amplitude for the trion formation from th…

[Phys. Rev. A 79, 053633] Published Wed May 20, 2009

We calculate the ground-state properties of fermionic dipolar atoms or molecules in a one-dimensional double-tube potential by using the Luttinger liquid theory and the density matrix renormalization-group calculation. When the external field is applied near a magic angle with respect to the double-…

[Phys. Rev. A 79, 053630] Published Tue May 19, 2009

We study the stability of Bose-Einstein condensate (BEC) with repulsive and attractive interatomic interactions in a harmonic plus quartic trap $\left[V\left(r\right)=\frac{1}{2}m{\omega }^2{r}^2+\lambda r^4\right]$. We find that BEC with repulsive interaction becomes more stable for $\lambda >0$. For $\lambda <0$, we observe a different metastability of the cond…

[Phys. Rev. A 79, 053629] Published Mon May 18, 2009

We consider dynamics of a slowly time-dependent Dicke model, which represents a many-body generalization of the Landau-Zener model. In particular, the model describes narrow Feshbach resonance passage in an ultracold gas of Fermi atoms. Adiabaticity is destroyed when a parameter crosses a critical v…

[Phys. Rev. A 79, 055602] Published Mon May 18, 2009

A necessary condition for the existence of a skyrmion in two-component Bose-Einstein condensates with SU(2) symmetry was recently provided by two of the authors [I. F. Herbut and M. Oshikawa, Phys. Rev. Lett. 97, 080403 (2006)], by mapping the problem to a classical particle in a potential subject t…

[Phys. Rev. A 79, 053626] Published Fri May 15, 2009

We study how well magnetic models can be implemented with ultracold bosonic atoms of two different hyperfine states in an optical superlattice. The system is captured by a two-species Bose-Hubbard model, but realizes in a certain parameter regime actually the physics of a spin-1/2 Heisenberg magnet,…

[Phys. Rev. A 79, 053627] Published Fri May 15, 2009

We investigate the lifetime of angular momentum in an ultracold strongly interacting Fermi gas, confined in a trap with controllable ellipticity. To determine the angular momentum we measure the precession of the radial quadrupole mode. We find that in the vicinity of a Feshbach resonance, the deepl…

[Phys. Rev. A 79, 053628] Published Fri May 15, 2009

With a recently developed time-evolving block decimation algorithm, we numerically study the ground-state quantum phase diagram of Fermi mixtures with attractive interspecies interactions loaded in one-dimensional optical lattices. For our study, we adopt a general asymmetric Hubbard model with spec…

[Phys. Rev. A 79, 051604(R)] Published Thu May 14, 2009

Subradiance, i.e., the cooperative inhibition of spontaneous emission by destructive interatomic interference, can be realized in a cold atomic sample confined in a ring cavity and lightened by a two-frequency laser. The atoms, scattering the photons of the two laser fields into the cavity mode, rec…

[Phys. Rev. A 79, 053622] Published Thu May 14, 2009

In nearly all experiments with ultracold atoms time-of-flight pictures are the only data available. In this paper we present an analytical strong-coupling calculation for those time-of-flight pictures of bosons in a three-dimensional optical lattice in the Mott phase. This allows us to determine the…

[Phys. Rev. A 79, 053623] Published Thu May 14, 2009

We study the dynamics of a one-dimensional Bose-Einstein condensate located in a time-dependent double-well trapping potential. In particular we investigate the way the system discovers existence of a ground state created in the new deeper well. It was shown that the transfer of the system into the …

[Phys. Rev. A 79, 053624] Published Thu May 14, 2009

We consider a very asymmetric system of fermions with an interaction characterized by a positive scattering length only. The minority atoms pair and form a Bose-Einstein condensate of dimers, while the surplus fermions interact only indirectly through the exchange of Bogoliubov sound modes. This int…

[Phys. Rev. A 79, 053625] Published Thu May 14, 2009

We introduce an exactly solvable model for trapped three-color atom gases. Application to a system of cigar-shaped trapped cold fermions reveals a complex structure of breached pairing phases. We find two competing superfluid phases at weak and intermediate couplings, each with two-color pair conden…

[Phys. Rev. A 79, 051603(R)] Published Wed May 13, 2009

Formation of stationary three-dimensional (3D) wave patterns generated by a small pointlike impurity moving through a Bose-Einstein condensate with supersonic velocity is studied. Asymptotic formulae for a stationary far-field density distribution are obtained. Comparison with the three-dimensional …

[Phys. Rev. A 79, 053619] Published Wed May 13, 2009

We study fundamental and vortical solitons in disk-morphed Bose-Einstein condensates (BECs) subject to strong confinement along the axial direction. Starting from the three-dimensional (3D) Gross-Pitaevskii equation (GPE), we proceed to an effective two-dimensional (2D) nonpolynomial Schrödinger equ…

[Phys. Rev. A 79, 053620] Published Wed May 13, 2009

We use the Bogoliubov–de Gennes formalism to analyze the effects of rotation on the ground-state phases of harmonically trapped Fermi gases, under the assumption that quantized vortices are not excited. We find that the rotation breaks Cooper pairs that are located near the trap edge, and that this …

[Phys. Rev. A 79, 053621] Published Wed May 13, 2009

The equation of state of a weakly interacting two-dimensional Bose gas is studied at zero temperature by means of quantum Monte Carlo methods. Going down to as low densities as $n{a}^2\propto {10}^{-100}$ permits us to obtain agreement on beyond mean-field level between predictions of perturbative methods and direct…

[Phys. Rev. A 79, 051602(R)] Published Tue May 12, 2009

We study the dynamics of a vortex in an atomic Bose-condensed gas at finite temperature within the Zaremba-Nikuni-Griffin formalism. In a harmonically trapped pancake-shaped condensate, an off-centered vortex is known to decay by spiraling out toward the edge of the condensate. We quantify the depen…

[Phys. Rev. A 79, 053615] Published Tue May 12, 2009

We investigate the appearance of vortices and vortex lattices in two-dimensional, anisotropic, and rotating Bose-Einstein condensates. Once the anisotropy reaches a critical value, the positions of the vortex cores in the ground state are no longer given by an Abrikosov lattice geometry but by a lin…

[Phys. Rev. A 79, 053616] Published Tue May 12, 2009

The possibility of adiabatically cooling a spin-1 polar Bose gas to a spin-nematic phase is theoretically discussed. The relation between the order parameter of the final spin-nematic phase and the starting temperature of the spinor Bose gas is obtained both using the mean-field approach for high te…

[Phys. Rev. A 79, 053617] Published Tue May 12, 2009

We present a proof of principle demonstration of signal processing using atom-optical methods. A Bose-Einstein condensate diffracted by a phase shifted periodic potential realizes the discrete Fourier transform for several test signals. We demonstrate that the quantum probability distribution of out…

[Phys. Rev. A 79, 053618] Published Tue May 12, 2009

We explain the spin segregation seen at Duke in a two-component gas of ${}^6\text{L}\text{i}$ [X. Du, L. Luo, B. Clancy, and J. E. Thomas, Phys. Rev. Lett. 101, 150401 (2008)] as a mean-field effect describable via a collisionless Boltzmann equation. As seen in experiments, we find that slight differences in the trapp…

[Phys. Rev. A 79, 051601(R)] Published Mon May 11, 2009

Recent experiments on imbalanced fermion gases have proved the existence of a sharp interface between a superfluid and a normal phase. We show that, at the lowest experimental temperatures, a temperature difference between normal (N) and superfluid (SF) phases can appear as a consequence of the bloc…

[Phys. Rev. A 79, 053612] Published Fri May 08, 2009

The atomic current in the Fourier-synthesized optical lattices under a constant external force is investigated theoretically. Based on a two-band model, the atomic current is derived by solving the Boltzmann equations. We find that the stationary atomic current changes with the probability of Landau…

[Phys. Rev. A 79, 053613] Published Fri May 08, 2009

A model of two-species bosons moving on the sites of a lattice is studied at nonzero temperature, focusing on magnetic order and superfluid-insulator transitions. First, Landau theory is used to find the general structure of the phase diagram and in particular to demonstrate the presence of first-or…

[Phys. Rev. A 79, 053614] Published Fri May 08, 2009

The stability and collapse of fundamental unstaggered bright solitons in the discrete Schrödinger equation with the nonpolynomial on-site nonlinearity, which models a nearly one-dimensional Bose-Einstein condensate trapped in a deep optical lattice, are studied in the presence of the long-range dipo…

[Phys. Rev. A 79, 053609] Published Thu May 07, 2009

We investigate a Bose-Einstein condensate (BEC) held in a quasi-one-dimensional Wannier-Stark lattice which is a combination of linear potential with an accelerating optical lattice. It is demonstrated that the system can be reduced to a periodically driven Gross-Pitaevskii one, in which we find the…

[Phys. Rev. A 79, 053610] Published Thu May 07, 2009

We study the zero temperature mean-field phase diagram of the Bose-Hubbard model in the presence of local coupling between the bosons and an external bath. We consider a coupling that conserves the on-site occupation number, preserving the robustness of the Mott-insulator and superfluid phases. We s…

[Phys. Rev. A 79, 053611] Published Thu May 07, 2009

We describe interacting mixtures of ultracold bosonic and fermionic atoms in harmonically confined optical lattices. For a suitable choice of parameters we study the emergence of superfluid and Fermi-liquid (noninsulating) regions out of Bose-Mott and Fermi-band insulators due to finite boson and fe…

[Phys. Rev. A 79, 055601] Published Thu May 07, 2009

We investigate ferromagnetic ordering in an itinerant ultracold atomic Fermi gas with repulsive interactions and population imbalance. In a spatially uniform system, we show that at zero temperature the transition to the itinerant magnetic phase transforms from first to second order with increasing …

[Phys. Rev. A 79, 053606] Published Wed May 06, 2009

The ability to interferometrically detect inertial rotations via the Sagnac effect has been a strong stimulus for the development of atom interferometry because of the potential ${10}^{10}$ enhancement of the rotational phase shift in comparison to optical Sagnac gyroscopes. Here we analyze ballistic trans…

[Phys. Rev. A 79, 053607] Published Wed May 06, 2009

We study families of one-dimensional matter-wave bright solitons supported by the competition of contact and dipole-dipole (DD) interactions of opposite signs. Soliton families are found, and their stability is investigated in the free space and in the presence of an optical lattice (OL). Free-space…

[Phys. Rev. A 79, 053608] Published Wed May 06, 2009

We investigate theoretically the behavior of a one-dimensional interacting Bose-Fermi mixture with equal masses and equal repulsive interactions between atoms at finite temperature in the scheme of thermodynamic Bethe ansatz. Combining the Yang-Yang thermodynamic formalism with local-density approxi…

[Phys. Rev. A 79, 053604] Published Tue May 05, 2009

We use quantum Monte Carlo simulations to obtain zero-temperature state diagrams for strongly correlated lattice bosons in one and two dimensions under the influence of a harmonic confining potential. Since harmonic traps generate a coexistence of superfluid and Mott insulating domains, we use local…

[Phys. Rev. A 79, 053605] Published Tue May 05, 2009

The Ginzburg-Landau theory of a trapped Fermi gas with a BEC-BCS crossover is derived by the path-integral method. In addition to the standard Ginzburg-Landau equation, a second equation describing the total atom density is obtained. These two coupled equations are necessary to describe both homogen…

[Phys. Rev. A 79, 053602] Published Mon May 04, 2009

We discover an inherent mechanism for entanglement swap associated with sequential superradiance from an atomic Bose-Einstein condensate. Based on careful examinations with both analytical and numerical approaches, we conclude that as a result of the swap mechanism, Einstein-Podolsky-Rosen-type quan…

[Phys. Rev. A 79, 053603] Published Mon May 04, 2009

We consider an atomic Fermi gas confined in a uniform optical lattice potential, where the atoms can pair into molecules via a magnetic-field-controlled narrow Feshbach resonance. The phase diagram of the resulting atom-molecule mixture in chemical and thermal equilibria is determined numerically in…

[Phys. Rev. A 79, 053601] Published Fri May 01, 2009

We investigate the ground-state properties of anyons confined in one-dimensional optical lattices with a weak harmonic trap using the exact numerical method based on Jordan-Wigner transformation. It is shown that in the Bose limit $\left(\chi =1\right)$ and Fermi limit $\left(\chi =0\right)$ the momentum distributions are symmetric …

[Phys. Rev. A 79, 043633] Published Thu Apr 30, 2009

The unequivocal detection of entanglement between two distinct matter-wave pulses is a significant challenge that has yet to be experimentally demonstrated. We describe a realistic scheme to generate and detect continuous-variable entanglement between two atomic matter-wave pulses produced via degen…

[Phys. Rev. A 79, 043634] Published Thu Apr 30, 2009

Two-dimensional (2D) vector matter waves in the form of soliton-vortex and vortex-vortex pairs are investigated for the case of attractive intracomponent interaction in two-component Bose-Einstein condensates. Both attractive and repulsive intercomponent interactions are considered. By means of a li…

[Phys. Rev. A 79, 043629] Published Tue Apr 28, 2009

We demonstrate two atom interferometric schemes based on Kapitza-Dirac scattering in a magnetic trap. In the first method, two Kapitza-Dirac scattering pulses are applied with a small time delay between them. High contrast interference is observed both using a thermal cloud and a Bose-Einstein conde…

[Phys. Rev. A 79, 043630] Published Tue Apr 28, 2009

Dynamical instabilities in a ${}^{87}\text{R}\text{b}$ $F=1$ spinor Bose-Einstein condensate are used as a parametric amplifier of quantum spin fluctuations. We demonstrate the spectrum of this amplifier to be tunable, in quantitative agreement with theory. We quantify the microscopic spin fluctuations of the initially pa…

[Phys. Rev. A 79, 043631] Published Tue Apr 28, 2009

Traditional optical phase imprinting of matter waves is of a dynamical nature. Here we show that both Abelian and non-Abelian geometric phases can be optically imprinted onto matter waves, yielding a number of interesting phenomena such as wave-packet redirecting and wave-packet splitting. In additi…

[Phys. Rev. A 79, 043632] Published Tue Apr 28, 2009

Decoherence in simple experiments with Bose-Einstein condensates is of great importance for quantum engineering. We study a system of two colliding condensates in Fock and correlated states. During the collision some atoms are scattered out of the condensates, which leads to the decoherence. The qua…

[Phys. Rev. A 79, 043628] Published Mon Apr 27, 2009

We study suppression of the collapse and stabilization of matter-wave solitons by means of time-periodic modulation of the effective nonlinearity, using the nonpolynomial Schrödinger equation for Bose-Einstein condensate trapped in a tight cigar-shaped potential. By means of systematic simulations, …

[Phys. Rev. A 79, 045602] Published Mon Apr 27, 2009

We demonstrate that Berry phases may greatly affect the dynamics of spin-orbit-coupled Bose-Einstein condensates. The effective model Hamiltonian under consideration is shown to be equivalent to the $E\times \epsilon$ Jahn-Teller model first introduced in molecular physics. The corresponding conical intersection i…

[Phys. Rev. A 79, 043627] Published Fri Apr 24, 2009

We report on the experimental investigation of the response of a three-dimensional Bose-Einstein condensate (BEC) in the presence of a one-dimensional (1D) optical lattice. By means of Bragg spectroscopy we probe the band structure of the excitation spectrum in the presence of the periodic potential…

[Phys. Rev. A 79, 043623] Published Thu Apr 23, 2009

Ultracold clouds of dimeric molecules can dissociate into quantum mechanically correlated constituent atoms that are either both bosons or both fermions. We theoretically model the dissociation of two-dimensional anisotropic molecular condensates for which this difference manifests as complementary …

[Phys. Rev. A 79, 043624] Published Thu Apr 23, 2009