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Wyświetlanie 1-15 z 22
Tytuł:
Dynamic Structure Factor of Ultracold Bosons in Optical Lattice
Autorzy:
Zaleski, T.
Kopeć, T.
Powiązania:
https://bibliotekanauki.pl/articles/1398602.pdf
Data publikacji:
2016-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
03.75.Hh
05.30.Jp
67.85.Hj
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.
Źródło:
Acta Physica Polonica A; 2016, 130, 2; 564-568
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ultra-Cold Bosons in Optical Lattice: Time-of-Flight Imaging of Atom-Atom Correlations
Autorzy:
Zaleski, T.
Kopeć, T.
Powiązania:
https://bibliotekanauki.pl/articles/1431254.pdf
Data publikacji:
2012-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
03.75.Kk
05.30.Jp
67.85.Hj
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.
Źródło:
Acta Physica Polonica A; 2012, 121, 4; 796-800
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Cold Atomic Gases in Optical Lattices with Disorder
Autorzy:
Schulte, T.
Drenkelforth, S.
Kruse, J.
Ertmer, W.
Arlt, J. J.
Kantian, A.
Sanchez-Palencia, L.
Santos, L.
Sanpera, A.
Sacha, K.
Zoller, P.
Lewenstein, M.
Zakrzewski, J.
Powiązania:
https://bibliotekanauki.pl/articles/2044614.pdf
Data publikacji:
2006-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
03.75.Kk
03.75.Lm
05.30.Jp
64.60.Cn
Opis:
Cold atomic gases placed in optical lattices enable studies of simple condensed matter theory models with parameters that may be tuned relatively easily. When the optical potential is randomized (e.g. using laser speckle to create a random intensity distribution) one may be able to observe Anderson localization of matter waves for non-interacting bosons, the so-called Bose glass in the presence of interactions, as well as the Fermi glass or quantum spin glass for mixtures of fermions and bosons.
Źródło:
Acta Physica Polonica A; 2006, 109, 1; 89-99
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Conductivity of Strongly Correlated Bosons in the Simple Cubic Lattice - Magnetic Field and Hopping Anisotropy Effects
Autorzy:
Sajna, A.
Polak, T.
Micnas, R.
Powiązania:
https://bibliotekanauki.pl/articles/1386533.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
03.75.Lm
05.30.Jp
03.75.Nt
Opis:
We investigate optical conductivity in three dimensional system of bosons under strong magnetic field. In particular, we consider Bose Hubbard model in the strongly correlated limit, where Mott insulator phase emerges. For chosen rational number of magnetic flux per cell we show that response of the system gains complex peaks behavior on the order of frequency corresponding to on-site boson repulsive interaction. Moreover, when anisotropy in hopping energy for the direction parallel to magnetic field is tuned up, the non-monotonous behavior of the optical conductivity could appear. The obtained results can be experimentally probed in the system of ultracold atoms loaded on an optical lattice.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 448-450
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Quantum Bright Soliton in a Disorder Potential
Autorzy:
Sacha, K.
Delande, D.
Zakrzewski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1585122.pdf
Data publikacji:
2009-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
03.75.Lm
72.15.Rn
05.30.Jp
Opis:
At very low temperature, a quasi-one-dimensional ensemble of atoms with attractive interactions tend to form a bright soliton. When exposed to a sufficiently weak external potential, the shape of the soliton is not modified, but its external motion is affected. We develop in detail the Bogoliubov approach for the problem, treating, in a non-perturbative way, the motion of the center of mass of the soliton. Quantization of this motion allows us to discuss its long time properties. In particular, in the presence of a disordered potential, the quantum motion of the center of mass of a bright soliton may exhibit Anderson localization, on a localization length which may be much larger than the soliton size and could be observed experimentally.
Źródło:
Acta Physica Polonica A; 2009, 116, 5; 772-778
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Harmonically Trapped Bosons on the Sierpiński Carpet
Autorzy:
Rovenchak, A.
Powiązania:
https://bibliotekanauki.pl/articles/1535594.pdf
Data publikacji:
2010-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.30.Jp
67.85.-d
64.60.an
Opis:
An ideal Bose-gas confined in a harmonic potential is studied. The thermodynamic properties of the said system are obtained in a general case of D dimensions, where D can be fractional (this corresponds to, e.g., porous medium). For the critical temperature, expansions with respect to the number of particles in the system are obtained. Numerical study is made for D = ln8/ln3 corresponding to the dimensionality of the so-called Sierpiński carpet.
Źródło:
Acta Physica Polonica A; 2010, 118, 4; 531-533
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pseudospin Models of Superconductors with Very Short Coherence Length
Autorzy:
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/1860991.pdf
Data publikacji:
1994-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
05.30.Jp
71.28.+d
Opis:
We discuss a few models developed for description of superconductivity with very short coherence length and point out their formal equivalence to specific spin models, such as an anisotropic Heisenberg model (s = 1/2) with two- and four-spin exchange coupling and with fixed magnetization in the z-direction, an XY-Z model with single ion anisotropy and a Kondo-lattice model with anisotropic on-site exchange. New results concerning the phase diagram of the Hubbard model with strong attraction, the electromagnetic properties of systems with the first order superconducting transition and a possibility of local charge moment compensation in systems of coexisting bound pairs and itinerant electrons are presented.
Źródło:
Acta Physica Polonica A; 1994, 85, 1; 117-131
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Superconductivity, Charge Orderings and Phase Separations in Systems with Local Electron Pairing
Autorzy:
Robaszkiewicz, S.
Pawłowski, G.
Powiązania:
https://bibliotekanauki.pl/articles/1946347.pdf
Data publikacji:
1996-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
05.30.Jp
71.28.+d
Opis:
We study two effective models developed for description of superconductors with short-coherence length: (i) the extended Hubbard model with on-site attraction and intersite repulsion, (ii) the model of hard-core charged bosons on a lattice. The analysis is concentrated on the problem of phase separations and competition between superconductivity (SS) and charge-density-wave (CDW) orderings. The phase diagrams of the systems are shown to consist of at least seven different states, including 3 types of phase separated (PS) states: CDW-SS (PS1), CDW-normal (PS2) and the state of electron droplets (PS3). By taking into account the PS states and the effects of longer-range density-density interactions (beyond nearest neighbors) our paper substantially generalizes and modifies the conclusions of previous papers concerning the models considered.
Źródło:
Acta Physica Polonica A; 1996, 90, 3; 569-586
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Bose-Hubbard Model in the Rotating Frame of Reference
Autorzy:
Polak, T.
Kopeć, T.
Powiązania:
https://bibliotekanauki.pl/articles/1536643.pdf
Data publikacji:
2010-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.30.Jp
03.75.Lm
03.75.Nt
Opis:
Following a novel experimental arrangement which can rotate a two-dimensional optical lattice at frequencies up to several kilohertz we discuss the ground state of the two-dimensional Bose-Hubbard Hamiltonian, relevant for rotating gaseous Bose-Einstein condensates, by employing U(1) quantum rotor approach and the topologically constrained path integral. Ultracold atoms in such a rotating lattice can be used for the direct quantum simulation of strongly correlated systems under large effective magnetic fields. We derive an effective quantum action for the Bose-Hubbard model, which enables a non-perturbative treatment of the zero-temperature phase transition in the rotating frame. We calculate the ground-state phase diagram, analytically deriving maximum repulsive energy for several rational values of the frustration rotation parameter f = 0, 1/2, 1/3, 1/4, and 1/6 for the square and triangular lattice. Performed calculations revealed strong non-monotonical dependence of the critical ratio of the kinetic energy to the repulsive on-site energy, that separates the global coherent from the insulating state, on topology of the lattice.
Źródło:
Acta Physica Polonica A; 2010, 118, 2; 279-282
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fermionic Mediated Effective Interaction for the Two-Dimensional Bose-Fermi Mixtures under Artificial Magnetic Field
Autorzy:
Polak, T.
Powiązania:
https://bibliotekanauki.pl/articles/1429103.pdf
Data publikacji:
2012-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.30.Jp
03.75.Lm
03.75.Nt
Opis:
The strongly interacting bosonic and non-interacting fermionic mixtures of diluted gases are studied. An artificial magnetic field is introduced in theory by imposing a Peierls phase shift on the wave functions of the constituents. A highly nontrivial limit of the quantum-Hall limit is achieved which provides oscillations effects of the fermion mediated interaction between bosons. In consequence the effective interaction between bosons can change the magnitude and sign. This provides possible explanations of the bosonic coherence loss observed experimentally in the "time of flight" and "peak width" experiments.
Źródło:
Acta Physica Polonica A; 2012, 121, 5-6; 1308-1311
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Lost of Bosonic Coherence Due to the Fermionic Presence Under the Synthetic Magnetic Field
Autorzy:
Polak, T.
Powiązania:
https://bibliotekanauki.pl/articles/1431224.pdf
Data publikacji:
2012-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.30.Jp
03.75.Lm
03.75.Nt
Opis:
We have studied effects of inter-species interaction of the bosons in a Bose-Fermi mixture over a large regime of particle numbers under the synthetic magnetic field. Analytically derived formulas for the density of states for several values of the magnetic fields f=1/2,1/3,1/4,1/6,1/8 and 3/8 allows us to calculate, with a very good accuracy, the effective interaction between bosons. The presence of the Hofstadter butterfly spectrum and fermionic species induces alternating sign potential between neutral bosonic atoms. Consequently bosons can attract or repulse each other whether sign of it strongly depends on the strength of the magnetic field applied to the sample.
Źródło:
Acta Physica Polonica A; 2012, 121, 4; 759-763
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Neutral Bosonic Condensates in Layered 2D Structures under Artificial Magnetic Field
Autorzy:
Polak, T.
Zaleski, T.
Powiązania:
https://bibliotekanauki.pl/articles/1429105.pdf
Data publikacji:
2012-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.30.Jp
03.75.Lm
03.75.Nt
Opis:
We show that the properties of the ideal Bose gas in three-dimensional optical lattice can be closely mimicked by finite two dimensional systems with only ten of layers. The match between critical properties strongly depends on the anisotropy of the hopping amplitudes in and between layers which we fully control. The theory we provided can be directly used in the experiments and results in less challenging requirements of the setups. We also present the phase diagram with its non-monotonic dependence of the ratio of tunneling to on-site repulsion when artificial magnetic field is applied to the system.
Źródło:
Acta Physica Polonica A; 2012, 121, 5-6; 1312-1314
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase Transitions in Optical Lattices at Finite Temperatures
Autorzy:
Polak, T.
Kopeć, T.
Powiązania:
https://bibliotekanauki.pl/articles/1810621.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.30.Jp
03.75.Lm
03.75.Nt
67.40.Kh
Opis:
We discuss the finite-temperature phase diagram in three-dimensional Bose-Hubbard model relevant for the Bose-Einstein condensates in optical lattices, by employing U(1) quantum rotor approach and the topologically constrained path integral, that includes a summation over U(1) topological charge. The effective action formalism allows us to formulate a problem in the phase only action and obtain analytical formulae for the critical lines beyond mean-field theory.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 418-420
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Quantum Rotor Approach to the Mott-Insulator Transition in the Bose-Hubbard Model
Autorzy:
Polak, T.
Kopeć, T.
Powiązania:
https://bibliotekanauki.pl/articles/1812265.pdf
Data publikacji:
2008-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.30.Jp
03.75.Lm
03.75.Nt
Opis:
We present the novel approach to the Bose-Hubbard model using the U(1) quantum rotor description. We formulate a problem in the phase only action using an effective action formalism and obtain analytical formulae for the critical lines. We show that the nontrivial U(1) phase field configurations have an impact on the phase diagrams. The topological character of the quantum field is governed by terms of the integer charges -- winding numbers n. The comparison of the presented results with recently obtained quantum Monte Carlo numerical calculations suggests that the competition between quantum effects in strongly interacting boson systems is correctly captured by our model.
Źródło:
Acta Physica Polonica A; 2008, 114, 1; 29-34
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Superconducting Properties and Phase Separation Effects in Systems with Local Pairing
Autorzy:
Pawłowski, G.
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/1955833.pdf
Data publikacji:
1997-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.-d
74.20.-z
05.30.Jp
Opis:
We examine the phase separation effects in a class of models developed for description of superconductors with local electron pairing: (i) the extended attractive Hubbard model, (ii) the model of hard-core charged bosons on a lattice. We analyse the behaviour of various superfluid characteristics as well as the evolution of the phase diagrams with increasing external magnetic field.
Źródło:
Acta Physica Polonica A; 1997, 91, 2; 409-413
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 22

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