arXiv subjects

Maxim Olshanii

Publications and source records attributed to Maxim Olshanii.

65 records · Page 4Linked to original sources

arXiv2005

Interferometry in dense nonlinear media and interaction-induced loss of contrast in microfabricated atom interferometers

In this paper we update the existing schemes for computation of atom-interferometric signal in single-atom interferometers to interferometry with dense Bose-condensed atomic samples. Using the theory developed we explain the fringe contrast degradation observed, for longer duration of interferometric cycle, in the Michelson interferometer on a chip recently realized at JILA (Ying-Ju Wang, Dana Z. Anderson, Victor M. Bright, Eric A. Cornell, Quentin Diot, Tetsuo Kishimoto, Mara Prentiss, R. A. Saravanan, Stephen R. Segal, Saijun Wu, Phys. Rev. Lett. 94, 090405 (2005)). We further suggest several recipes for suppression of the interaction-related contrast degradation.

cond-mat.other↗

arXiv2004

No-soliton--soliton phase transition in a trapped one-dimensional Bose gas

Following the experimental observation of bright matter-wave solitons [L. Khaykovich et al., Science v. 296, 1290 (2002); K. E. Strecker et al., Nature (London) v. 417, 150 (2002)], we develop a semi-phenomenological theory for soliton thermodynamics and find the condensation temperature. Under a modified thermodynamic limit, the condensate occupation at the critical temperature undergoes a sudden jump to a nonzero value, indicating a discontinuous phase transition. Treating the condensation as a diffusion over a barrier shows that the condensation time is exponentially long as one approaches the thermodynamic limit, and the longest near the critical temperature.

cond-mat.soft↗

arXiv2003

Short-Distance Correlation Properties of the Lieb-Liniger System and Momentum Distributions of Trapped One-Dimensional Atomic Gases

We derive exact closed form expressions for the first few terms of the short-distance Taylor expansion of the one-body correlation function of the Lieb-Liniger gas. As an intermediate result we obtain the high-p asymptotics of the momentum distribution of both free and harmonically trapped atoms and show that it obeys a universal 1/p^4 law for_all_ values of the interaction strength. We discuss the ways to observe the predicted momentum distributions experimentally, regarding them as a sensitive identifier for the Tonks-Girardeau regime of strong correlations.

cond-mat↗

arXiv2003

Schemes for loading a Bose-Einstein condensate into a two-dimensional dipole trap

We propose two loading mechanisms of a degenerate Bose gas into a surface trap. This trap relies on the dipole potential produced by two evanescent optical waves far detuned from the atomic resonance, yielding a strongly anisotropic trap with typical frequencies 40 Hz x 65 Hz x 30 kHz. We present numerical simulations based on the time-dependent Gross-Pitaevskii equation of the transfer process from a conventional magnetic trap into the surface trap. We show that, despite a large discrepancy between the oscillation frequencies along one direction in the initial and final traps, a loading time of a few tens of milliseconds would lead to an adiabatic transfer. Preliminary experimental results are presented.

cond-mat↗

arXiv2002

Producing Bose condensates using optical lattices

We relate the entropies of ensembles of atoms in optical lattices to atoms in simple traps. We then determine which ensembles of lattice-bound atoms will adiabatically transform into a Bose condensate. This shows a feasible approach to Bose condensation without evaporative cooling.

cond-mat↗

arXiv2002

A Closed Class of Hydrodynamical Solutions for the Collective Excitations of a Bose-Einstein Condensate

A trajectory approach is taken to the hydrodynamical treatment of collective excitations of a Bose-Einstein condensate in a harmonic trap. The excitations induced by linear deformations of the trap are shown to constitute a broad class of solutions that can be fully described by a simple nonlinear matrix equation. An exact closed-form expression is obtained for the solution describing the mode {n=0, m=2} in a cylindrically symmetric trap, and the calculated amplitude-dependent frequency shift shows good agreement with the experimental results of the JILA group.

cond-mat↗

arXiv2002

Rigorous approach to the problem of ultraviolet divergencies in dilute Bose gases

We have found an expression for the full many-body Green's function of N pairwise finite-range interacting atoms, in a form of a chain fraction involving two-body T-matrices only, with no explicit presence of the interaction potentials themselves. We show that in the limit of infinitely small potential range, this expression reduces to the Green's function for N atoms interacting via a generalized pseudo-potential, function of a free parameter Λ. Using this Λ-freedom we resolve all inconsistensies of the Hartree-Fock-Bogoliubov formalism known so far, with no ad hoc modifications of the theory.

cond-mat↗

arXiv2001

Field-Induced Magnetic Order in Quantum Spin Liquids

We study magnetic field-induced three-dimensional ordering transitions in low-dimensional quantum spin liquids, such as weakly coupled, antiferromagnetic spin-1/2 Heisenberg dimers and ladders. Using stochastic series expansion quantum Monte Carlo simulations, thermodynamic response functions are obtained down to ultra-low temperatures. We extract the critical scaling exponents which dictate the power-law dependence of the transition temperature on the applied magnetic field. These are compared with recent experiments on candidate materials and with predictions for the Bose-Einstein condensation of magnons obtained in mean-field theory.

cond-mat.str-el↗

arXiv2001

Bosons in cigar-shape traps: Thomas-Fermi regime, Tonks-Girardeau regime, and between

We present a quantitative analysis of the experimental accessibility of the Tonks-Girardeau gas in the current day experiments with cigar-trapped alkalis. For this purpose we derive, using a Bethe anzats generated local equation of state, a set of hydrostatic equations describing one-dimensional delta-interacting Bose gases trapped in a harmonic potential. The resulting solutions cover the_entire range_ of atomic densities.

cond-mat↗

arXiv1998

Finite-Temperature Collective Excitation of a Bose-Einstein Condensate

We derive a simple formula for the finite-temperature shifts of the collective excitations of a Bose-Einstein condensate. To test the validity of our treatment we apply it to explain the anomalous behavior of the ``m=2'' excitation frequency in the recent JILA experiments (D. S. Jin et al, PRL, 78 (1997) 764), where this frequency does not approach its ``noninteracting'' value at $ω= 2 ω_ρ$ but, instead, decreases with temperature. It turns out that the effect is mainly governed by a resonance between the condensate excitation frequency and one of the quantum eigenfrequencies of the thermal cloud. Comparison of our predictions with the JILA experimental data shows a good agreement.

cond-mat↗

arXiv1998

Atomic Scattering in Presence of an External Confinement and a Gas of Impenetrable Bosons

We calculate, within the pseudopotential approximation, a one-dimensional scattering amplitude and effective one-dimensional interaction potential for atoms confined transversally by an atom waveguide or highly elongated ``cigar''-shaped atomic trap. We show that in the low-energy scattering regime, the scattering process degenerates to a total reflection suggesting an experimental realization of a famous model in theoretical physics - a one-dimensional gas of impenetrable bosons (``Tonks'' gas). We give an estimate for suitable experimental parameters for alkali atoms confined in waveguides.

cond-mat↗