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1
Content available remote

Chaos Assisted Tunneling and Nonspreading Wave Packets

100%
Zakrzewski J., Delande D., Buchleitner A.
Acta Physica Polonica A
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1998
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vol. 93
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issue 1
179-186
EN
Consider an initial state lying on a primary resonance island. The state may tunnel into the chaotic sea surrounding it and further escape to infinity via chaotic diffusion. Properties of transport in such a situation are studied on an exemplary system - the hydrogen atom driven by microwaves. We show that the combination of tunneling followed by chaotic diffusion leads to peculiar large scale fluctuations of the AC Stark shift and ionization rates. An appropriate random matrix model describes accurately these statistical properties.
2
Content available remote

Extracting Information from Non Adiabatic Dynamics: Excited Symmetric States of the Bose-Hubbard Model

100%
Łącki M., Delande D., Zakrzewski J.
Acta Physica Polonica A
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2011
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vol. 120
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issue 6A
A-178-A-184
EN
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.
3
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Quantum Bright Soliton in a Disorder Potential

100%
Sacha K., Delande D., Zakrzewski J.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
772-778
EN
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.
4
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Role of Correlations and Off-Diagonal Terms in Binary Disordered One-Dimensional Systems

100%
Kosior A., Major J., Płodzień M., Zakrzewski J.
Acta Physica Polonica A
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2015
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vol. 128
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issue 6
1002-1007
EN
We investigate one-dimensional tight binding model in the presence of a correlated binary disorder. The disorder is due to the interaction of particles with heavy immobile other species. Off-diagonal disorder is created by means of a fast periodic modulation of interspecies interaction. The method based on transfer matrix techniques allows us to calculate the energies of extended modes in the correlated binary disorder. We focus on N-mer correlations and regain known results for the case of purely diagonal disorder. For off-diagonal disorder we find resonant energies. We discuss ambiguous properties of those states and compare analytical results with numerical calculations. Separately we describe a special case of the dual random dimer model.
5
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Many-Body Localization for Randomly Interacting Bosons

100%
Sierant P., Delande D., Zakrzewski J.
Acta Physica Polonica A
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2017
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vol. 132
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issue 6
1707-1712
EN
We study many-body localization in a one dimensional optical lattice filled with bosons. The interaction between bosons is assumed to be random, which can be realized for atoms close to a microchip exposed to a spatially fluctuating magnetic field. Close to a Feshbach resonance, such controlled fluctuations can be transfered to the interaction strength. We show that the system reveals an inverted mobility edge, with mobile particles at the lower edge of the spectrum. A statistical analysis of level spacings allows us to characterize the transition between localized and excited states. The existence of the mobility edge is confirmed in large systems, by time dependent numerical simulations using tDMRG. A simple analytical model predicts the long time behavior of the system.
6
Content available remote

Nonsequential Double Ionization of Atoms in Strong Laser Pulses

100%
Prauzner-Bechcicki J., Sacha K., Eckhardt B., Zakrzewski J.
Acta Physica Polonica A
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2007
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vol. 112
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issue 4
699-706
EN
It is now possible to produce laser pulses with reproducible pulse shape and controlled carrier envelope phase. It is discussed how that can be explored in double ionisation studies. To this end we solve numerically the Schrödinger equation for a limited dimensionality model which nevertheless treats electron repulsion qualitatively correctly and allows to study correlation effects due to the Coulomb repulsion.
7
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Luminescence Quantum Efficiency of Mn^{2+} States in ZnSe:Mn as Studied by means of Photoacoustic Spectroscopy

76%
Męczyńska H., Łęgowski S., Dąbrowska W., Popielarski M., Ogielski Z., Zakrzewski J.
Acta Physica Polonica A
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1993
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vol. 84
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issue 4
823-825
EN
The photoacoustic spectroscopy with a piezoelectric transducer was employed to determined the quantum efficiency for low Mn concentration in ZnSe monocrystals. The photoacoustic spectra were measured using the continuous wave excitation and nanosecond pulse method.
8
Content available remote

Photoluminescence and Photoacoustic Investigations of Beryllium and Magnesium Containing Wide Gap II-VI Mixed Crystals

76%
Firszt F., Łęgowski S., Męczyńska H., Sekulska B., Szatkowski J., Zakrzewski J., Paszkowicz W.
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vol. 95
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issue 6
991-996
EN
Zn_{1-x}Be_{x}Se, Cd_{1-x}Mg_{x}Se and Zn_{1-x-y}Be_{x}Mg_{y}Se mixed crystals grown from the melt with different concentrations of Be and Mg have been characterized by photoluminescence and photoacoustic methods. An increase in band gap energy with increasing Be and Mg contents was observed. The photoacoustic spectroscopy was also employed for evaluation of thermal diffusivity of mixed Zn_{1-x}Be_{x}Se crystals with different beryllium contents.
9
Content available remote

Photoacoustic Investigation of Absorption Edge of Cd_{1-x}Mg_{x}Se Mixed Crystals

76%
Firszt F., Łęgowski S., Męczyńska H., Sekulska B., Szatkowski J., Zakrzewski J., Paszkowicz W.
Acta Physica Polonica A
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1997
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vol. 92
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issue 4
749-752
EN
The Cd_{1-x}Mg_{x}Se crystals were grown by modified Bridgman method for x ranging from 0 to 0.44. The photoacoustic spectroscopy was employed for evaluation of the band gaps of series Cd_{1-x}Mg_{x}Se mixed crystals with different composition. The photoacoustic spectra were measured at 300 K and 90 K using continuous wave excitation in the range from 400 nm to 800 nm. The increase in the band-gap energy with increasing Mg content is observed. The photoacoustic results are compared with photoluminescence and transmission spectra.
10
Content available remote

Optical and Structural Properties of Zn_{1-x}Be_{x}Se Mixed Crystals

64%
Firszt F., Łęgowski S., Męczyńska H., Szatkowski J., Zakrzewski J., Paszkowicz W., Domagała J., Marczak M.
Acta Physica Polonica A
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1998
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vol. 94
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issue 2
309-312
EN
Optical and structural properties of Zn_{1-x}Be_{x}Se bulk crystals in the range of composition 0 ≤ x ≤ 0.41 have been studied. These crystals were grown by Bridgman method under an argon overpressure. Transmission, absorption, photoluminescence and photoacoustic spectra as a function of composition were investigated. It has been found that the crystal structure is of sphalerite type. The crystal quality increases when the crystallization process of the same boule is performed more than once. In the investigated composition range the lattice constant decreases and the energy gap increases with increasing beryllium content. From photoluminescence measurements the excitonic energy gap about 3.64 eV at 40 K was estimated for the highest obtained Be concentration (x=0.41).
11
Content available remote

A Photoacoustic Study of Zn_{1-x}Mg_{x}Se Mixed Crystals

64%
Męczyńska H., Zakrzewski J., Łęgowski S., Popielarski M., Firszt F., Szatkowski J., Klugiewicz R., Łęgowski K.
Acta Physica Polonica A
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1995
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vol. 87
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issue 2
547-550
EN
The photoacoustic spectroscopy with a piezoelectric transducer was em­ployed to evaluate the band gaps of a series of Zn_{1-x}Mg_{x}Se mixed crystals of different composition. The photoacoustic measurements performed at room temperature yield information about the quality of the samples. The photoa­coustic spectra were measured using the continuous wave and nanosecond pulse excitation.
12
Publication available in full text mode
Content available

Cold Atomic Gases in Optical Lattices with Disorder

52%
Schulte T., Drenkelforth S., Kruse J., Ertmer W., Arlt J., Kantian A., Sanchez-Palencia L., Santos L., Sanpera A., Sacha K., Zoller P., Lewenstein M., Zakrzewski J.
Acta Physica Polonica A
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2006
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vol. 109
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issue 1
89-99
EN
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.
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