Temat: 67.85.Hj - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Phase Transitions of Bosons in Optical Lattices with a Mixture of Single and Pair Hoppings
Autorzy:: Travin, V.
Kopeć, T.
Tematy:: 67.10.Fj
67.85.Hj
67.90.+z; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1398644.pdf Link otwiera się w nowym oknie
Opis:: We considered Bose condensate in optical lattice with mixture of single and pair hoppings for arbitrary temperatures. In order to calculate free energy of the system and determine phase transition lines between disordered and ordered phases, the Laplace transform method has been applied. We identified several possible scenarios for phase diagrams with phase transitions of the second kind. The results have been obtained from both analytical and numerical methods of calculation. Finally, we obtained thermal insensitivity of the system for big values of reduced pair hopping and (or) reduced chemical potential.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Effect of Dimple Potential on Ultraslow Light in a Bose-Einstein Condensate
Autorzy:: Tarhan, D.
Uncu, H.
Tematy:: 42.50.Gy
67.85.Hj; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1490935.pdf Link otwiera się w nowym oknie
Opis:: We investigate the propagation of ultraslow optical pulse in atomic Bose-Einstein condensate in a harmonic trap decorated with a dimple potential. The role of dimple potential on the group velocity and time delay is studied. Since we consider the interatomic scattering interactions, nonlinear Schrödinger equation or the Gross-Pitaevskii equation is used in order to get the density profile of the atomic system. We find large group delays of order 1 ms in an atomic Bose-Einstein condensate in a harmonic trap with a deep dimple potential.
Dostawca treści:: Biblioteka Nauki

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na półce

Skocz do pozycji: 3.

Tytuł:: Dynamic Structure Factor of Ultracold Bosons in Optical Lattice
Autorzy:: Zaleski, T.
Kopeć, T.
Tematy:: 03.75.Hh
05.30.Jp
67.85.Hj; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1398602.pdf Link otwiera się w nowym oknie
Opis:: Ultracold atoms in optical lattices have been intensively investigated in recent years as they provide a very well controllable environment for observation of many-body quantum phenomena, closely mimicking physics of strongly interacting electronic systems. Here, we use the quantum rotor approach supplemented by the Bogolyubov method to investigate one- and two-particle excitations, which are a measure of inter-particle correlations. We calculate one-particle spectral function and dynamic structure factor, which can be observed using spectroscopy of cold atomic systems. Our calculations require a significant numerical effort to determine multidimensional convolutions of momentum and frequency dependent constituents functions, which we achieve using parallelised fast Fourier transform. We observe the appearance of sharp coherence peaks in the superfluid phase of the cold bosons, which closely resembles the formation of sharply defined quasiparticle excitations below $T_{c}$ in cuprates or smeared excitation spectra characteristic for strongly interacting systems.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Phase Diagram of Mixtures of Ultracold Bosons in Optical Lattice
Autorzy:: Anufriiev, S.
Zaleski, T.
Tematy:: 03.75.Hh
05.30.Jp
67.85.Hj; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1398645.pdf Link otwiera się w nowym oknie
Opis:: We study a behaviour of mixture of two species of ultracold bosons trapped in optical lattice. Using mean-field approximation, we determine the phase diagram of the system for wide range of parameters. We observe that each of the groups of atoms can condense into superfluid state or localize and form the Mott insulator, which yields that the whole system is either superfluid, the Mott insulator, or a mixed state. It appears that introduction of interaction between different kinds of atoms can strongly renormalise the phase diagram. It can alter the critical behaviour modifying multi-criticality of crossing points and order of phase transitions between mixed and superfluid states.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Ultra-Cold Bosons in Optical Lattice: Time-of-Flight Imaging of Atom-Atom Correlations
Autorzy:: Zaleski, T.
Kopeć, T.
Tematy:: 03.75.Kk
05.30.Jp
67.85.Hj; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1431254.pdf Link otwiera się w nowym oknie
Opis:: In the present paper, we investigate a system of strongly interacting bosons confined in two-dimensional optical lattice. We propose a combination of the Bogoliubov method with the quantum rotor approach and determine the spatial atom-atom correlations. This allows us to calculate time-of-flight absorption images, which exhibit all the characteristic features present in experimental results, namely transition from superfluid peaks to Mott insulating blob.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Extracting Information from Non Adiabatic Dynamics: Excited Symmetric States of the Bose-Hubbard Model
Autorzy:: Łącki, M.
Delande, D.
Zakrzewski, J.
Tematy:: 67.85.Hj
03.75.Kk
03.75.Lm; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1492502.pdf Link otwiera się w nowym oknie
Opis:: Using Fourier transform on a time series generated by unitary evolution, we extract many-body eigenstates of the Bose-Hubbard model corresponding to low energy excitations, which are generated when the insulator-superfluid phase transition is realised in a typical experiment. The analysis is conducted in a symmetric external potential both without and with a disorder. A simple classification of excitations in the absence disorder is provided. The evolution is performed assuming the presence of the parity symmetry in the system rendering many-body quantum states either symmetric or antisymmetric. Using symmetry-breaking technique, those states are decomposed into elementary one-particle processes.
Dostawca treści:: Biblioteka Nauki

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na półce

Skocz do pozycji: 7.

Tytuł:: Role of bandwidths and energy gap in formation of ground state of ultra-cold bosons in artificial magnetic fields
Autorzy:: Patucha, K.
Grygiel, B.
Zaleski, T.
Tematy:: 67.85.Hj
05.30.Jp
03.75.Lm; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1062004.pdf Link otwiera się w nowym oknie
Opis:: We study the properties of ultra-cold bosons in optical lattice in arbitrary gauge potentials. Using quantum rotor approach we are able to go beyond mean-field approximation thus taking into account subtleties of the band structure of the artificial magnetic field. This allows us to elucidate the interplay of the subbands widths and energy gaps on the formation of the coherent state. As a result, we are able to pinpoint the elements of the band structure, which are crucial to proper theoretical description of the synthetic magnetic field in a lattice bosonic system. This leads us finally to a method of approximation of the Hofstadter butterfly spectrum with a simpler band structure and use it to investigate the ground state of the system for a wide range of magnetic fluxes.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Optical Conductivity of Ultra-Cold Bosons in Optical Lattices
Autorzy:: Grygiel, B.
Patucha, K.
Zaleski, T.
Tematy:: 67.85.Hj
05.30.Jp
03.75.Lm; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1398646.pdf Link otwiera się w nowym oknie
Opis:: We study ultra-cold bosonic systems in optical lattice using quantum rotor approach to calculate the current-current correlations, which provides the information about conductivity of the system. The method allows us to go beyond mean-field approximation and track the behavior of the real part of the conductivity along the phase transition between the Mott insulator and superfluid state for various geometries of the lattice. In the phase-ordered state at zero temperature, a discrete ingredient appears resulting from the long-range coherence in the system.
Dostawca treści:: Biblioteka Nauki

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na półce

Skocz do pozycji: 9.

Tytuł:: Dimensional Reduction and Localization of a Bose-Einstein Condensate in a Quasi-1D Bichromatic Optical Lattice
Autorzy:: Salasnich, L.
Adhikari, S.
Tematy:: 03.75.Nt
03.75.Lm
64.60.Cn
67.85.Hj; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1190087.pdf Link otwiera się w nowym oknie
Opis:: We analyze the localization of a Bose-Einstein condensate in a one-dimensional bichromatic quasi-periodic optical-lattice potential by numerically solving the 1D Gross-Pitaevskii equation (1D GPE). We first derive the 1D Gross-Pitaevskii equation from the dimensional reduction of the 3D quantum field theory of interacting bosons obtaining two coupled differential equations (for axial wave fuction and space-time dependent transverse width) which reduce to the 1D Gross-Pitaevskii equation under strict conditions. Then, by using the 1D Gross-Pitaevskii equation we report the suppression of localization in the interacting Bose-Einstein condensate when the repulsive scattering length between bosonic atoms is sufficiently large.
Dostawca treści:: Biblioteka Nauki

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