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1
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Photoluminescence of Charged Excitons in Fractional Quantum Hall Systems

100%
Wójs A.
Acta Physica Polonica A
|
2004
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vol. 106
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issue 3
355-366
EN
Neutral and charged excitonic complexes formed in integral and fractional quantum Hall systems are discussed. They are bound states of a small number of charged quasiparticles (e.g., conduction electrons and valence holes, reversed-spin electrons and spin holes, Laughlin quasielectrons and quasiholes, composite fermions) that occur in an electron system under specific conditions (electron density, well width, electric and magnetic fields, etc.). The examples are interband neutral and charged excitons, "anyon excitons", spin waves, skyrmions, and "skyrmion excitons". Their possible decay processes include radiative recombination, experimentally observed in photoluminescence or far infrared emission, or spin transitions, important in the context of nuclear spin relaxation.
2
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Quantum Hall State ν = 1/3 and Antilexicographic Order of Partitions

64%
Kuśmierz B., Wójs A.
Acta Physica Polonica A
|
2016
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vol. 130
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issue 5
1183-1186
EN
We focus on a certain aspect of trial wave function approach in the fractional quantum Hall effect. We analyze the role of partition orderings and discuss the possible numerical search for the partition determining the subspace of the Hilbert space containing a particular quantum Hall wave function. This research is inspired by analogical properties of certain polynomials which are the object of interest of the symmetric function theory, especially the Jack polynomials (related to the so-called "Jack states"). Presented method may be used in the search of candidate trial wave functions. We also justify (in certain cases) diagonalization of the Coulomb repulsion Hamiltonian restricted to certain subspaces. We focus on the states at filling factor ν=1/3 in the lowest and second Landau level.
3
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Comparative Numerical Analysis of Quasi-Two-Dimensional Negative and Positive Trions in High Magnetic Fields

64%
Trojnar A., Wójs A.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1411-1416
EN
Exact diagonalization calculations in the Haldane spherical geometry are carried out for the three-body Coulomb problem in a quasi-two-dimensional quantum well, in the presence of perpendicular magnetic field. Simultaneous inclusion of several Landau levels and quantum well subbands in the configuration-interaction basis allowed for quantitative description of the coupling between the in-plane dynamics (governed by interplay of cyclotron quantization and Coulomb interactions) and single-particle excitations in the normal direction. The energy spectra of negative and positive trions are compared in symmetric and asymmetric wells with realistic widths and carrier concentrations. Effects of nearby impurities are also studied.
4
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Commutators of Jastrow Factors and Angular Momentum Operators

64%
Kuśmierz B., Wójs A.
Acta Physica Polonica A
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2017
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vol. 132
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issue 2
405-407
EN
We present detailed calculations of commutators of the Jastrow factor and certain differential operators useful in the fractional quantum Hall effect. In particular, we analyze action of the angular momentum operators projected from the Haldane sphere on an arbitrary composite fermions state. Examined L⁺ and L¯ momentum operators and following uniformity condition had proven to be useful in the search for candidates for quantum Hall ground states among many families of polynomials including the Jack polynomials.
5
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Spin Transition in a Correlated Liquid οf Composite Fermions

64%
Wójs A., Quinn J.
Acta Physica Polonica A
|
2009
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vol. 115
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issue 1
153-155
EN
We study spin polarization of the ν_e=4/11 fractional quantum Hall state corresponding to the ν=1/3 filling of the second composite fermion Landau level, and predict a spin phase transition in realistic systems.
6
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Calculation of Exciton and Trion Absorption Spectra in High Magnetic Fields

64%
Gładysiewicz A., Wójs A.
Acta Physica Polonica A
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2006
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vol. 110
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issue 2
183-188
EN
Density of states and absorption spectrum of narrow quantum wells containing a small number of free electrons and subject to a high magnetic field are calculated numerically. The effect of an additional, second electron on the photoexcited electron-hole pair is analyzed. In density of states, the exciton-electron interaction fills the gaps between the Landau levels and yields additional discrete peaks corresponding to bound trions. In absorption, interaction with the additional free electron has no effect on the position or intensity of the main sequence of excitonic peaks. However, it gives rise to additional weaker trion peaks, both in the lowest and higher Landau levels.
7
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Composite Fermions and the Fractional Quantum Hall Effect

64%
Wójs A., Quinn J.
Acta Physica Polonica A
|
1999
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vol. 96
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issue 5
593-602
EN
The mean field composite fermion picture successfully predicts low lying states of fractional quantum Hall systems. This success cannot be attributed to a cancellation between the Coulomb and Chern-Simons interactions beyond the mean field and solely depends on the short-range of the Coulomb pseudopotential in the lowest Landau level. The class of pseudopotentials for which the mean field composite fermion picture can be applied is defined. The success or failure of the mean field composite fermion picture in various systems (electrons in excited Landau levels, Laughlin quasiparticles, charged magnetoexcitons) is explained.
8
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Jack Polynomials and Fractional Quantum Hall Effect at ν = 1/3

64%
Kuśmierz B., Wójs A.
Acta Physica Polonica A
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2016
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vol. 130
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issue 2
607-608
EN
We investigate properties of strongly correlated, spinless electrons confined within given Landau level at filling factor ν = 1/3. Our analysis is based on the formalism of the Jack polynomials. Selected Jack polynomial wave functions are compared with ground states of the Coulomb interaction Hamiltonians, in different materials and the Landau levels, obtained by exact diagonalization. We show that certain Jack wave functions can be used as a description of fractional quantum Hall states.
9
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Quantum Dots - Theory for Experiments

52%
Jacak L., Krasnyj J., Wójs A.
Acta Physica Polonica A
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1997
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vol. 92
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issue 4
633-640
EN
A simple model based on the effective-mass method and treating a quantum dot as a small irregularity of the periodic crystal field is developed and used for the description of the radiative recombination of an exciton captured in that quasi-zero-dimensional structure. The additional peaks appearing in the photoluminescence spectra at the critical quantum dot size are predicted as a consequence of the metastable excited states occurring in the energy spectrum of a confined exciton. The obtained dependence of the photoluminescence spectrum on the dot size and magnetic field reproduces well the available experimental results.
10
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Many-Exciton Complexes in Self-Assembled Quantum Dots

52%
Wójs A., Hawrylak P., Jacak L.
Acta Physica Polonica A
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1996
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vol. 90
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issue 5
1108-1112
EN
The system of interacting electrons and holes confined in a lens-shaped InGaAs self-assembled dot is studied using exact diagonalization techniques. The single-particle energy spectrum of self-assembled dot is well approximated by that of a quasi-two-dimensional atom with parabolic lateral confinement. The electronic shell structure of self-assembled dot is responsible for a remarkable dependence of the absorption/emission spectrum on the number of excitons. This is explained in terms of hidden symmetries leading to a formation of coherent many-exciton states of weakly interacting excitons and bi-excitons.
11
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Trion Binding Energies and Wave Functions in Doped Quantum Wells

52%
Gładysiewicz A., Wójcik K., Wójs A., Quinn J.
Acta Physica Polonica A
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2005
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vol. 108
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issue 4
669-674
EN
The energy spectra of negative trions (X^-=2e+h) in one-sided doped GaAs quantum wells are calculated. The maps of the trion binding energyΔ as a function of well width w, electron concentration n, and the magnetic field B are obtained. The dependence of the trion ground state ("bright singlet" versus "dark triplet") on those parameters is established.
12
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Analysis of the Quantum Spin Hall and Quantum Anomalous Hall Effects in a Two-Dimensional Decorated Lattice Using Entanglement Spectrum

52%
Piekarska A., Potasz P., Wójs A.
Acta Physica Polonica A
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2016
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vol. 129
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issue 1a
A-87-A-89
EN
We study topological properties of a two-dimensional decorated lattice using entanglement spectrum and trace index. Using these measures, we distinguish various phases of the system predicted recently, including the quantum spin Hall effect and quantum anomalous Hall effect. The topologically trivial and non-trivial phases are identified, with assignment of a Chern number to each of the bands.
13
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Jack 3/5 State from Two-Body Interaction

52%
Kuśmierz B., Wu Y., Wójs A.
Acta Physica Polonica A
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2016
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vol. 129
|
issue 1a
A-73-A-74
EN
We investigate the Read-Rezayi parafermion state of correlated electrons at the fractional Landau level filling ν=3/5. It is a Jack polynomial generated by contact four-body repulsion. We show by exact diagonalization that it is also emerges from a suitable short-range two-body interaction. We find that it closely matches Coulomb ground state in the second Landau level of non-relativistic fermions, and thus possibly describes the ν=13/5 (and, by conjugation, ν=12/5) fractional quantum Hall effect in GaAs.
14
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Fractional Quantum Hall States with Non-Abelian Statistics

52%
Möller G., Wójs A., Cooper N.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
847-848
EN
Using exact numerical diagonalization we have studied correlated many-electron ground states in a partially filled second Landau level. We consider filling fractions ν = 1/2 and 2/5, for which incompressible quantum liquids with non-Abelian anion statistics have been proposed. Our calculations include finite layer width, Landau level mixing and arbitrary deformation of the interaction pseudopotential. Computed energies, gaps, and correlation functions support the non-Abelian ground states at both ν = 1/2 ("Pfaffian") and ν = 2/5 ("parafermion" state).
15
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Condensation of Nonabelian Moore-Read Quasiholes in Correlated Composite Fermion Liquids

52%
Wodziński D., Wójs A., Quinn J.
Acta Physica Polonica A
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2006
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vol. 110
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issue 3
417-422
EN
Two- and three-body correlation functions (number of pairs or triplets vs. relative angular momentum) of electrons or Laughlin quasielectrons (i.e., composite fermions in their first excited Landau level) are studied numerically in several fractional quantum Hall liquids. It is shown directly that theν_e=4/11 liquid (corresponding to aν=1/3 filling of composite fermions in their first excited Landau level) is a paired state of quasielectrons, hence interpreted as a condensate of "second-generation" quasiholes of Moore-Readν=1/2 state of composite fermions.
16
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Fractional Quasiexcitons in Photoluminescence of Quantum Hall Liquids

52%
Wójs A., Gładysiewicz A., Quinn J.
Acta Physica Polonica A
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2005
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vol. 108
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issue 5
923-928
EN
Realistic calculations of photoluminescence spectra for a 20 nm quantum well at a filling factorν=1/3 are presented. The new states formed from charged excitons (trions) by correlation with the surrounding electrons are identified. These "quasiexcitons" differ from usual excitons and trions by having fractionally charged constituents. Their binding energies and emission intensities depend on the involved trion, leading to discontinuity in photoluminescence.
17
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Pairing and Condensation of Laughlin Quasiparticles in Fractional Quantum Hall Systems

52%
Wójs A., Yi K., Quinn J.
Acta Physica Polonica A
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2003
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vol. 103
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issue 6
517-523
EN
From the analysis of their interaction pseudopotentials, it is argued that (at certain filling factors) Laughlin quasiparticles can form pairs. It is further proposed that such pairs could have Laughlin correlations with one another and form condensed states of a new type. The sequence of fractions corresponding to these states includes all new fractions observed recently in experiment (e.g.,ν=5/13, 3/8, or 4/11).
18
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Pair-Distribution Functions of Laughlin Quasielectrons in Partially Filled Composite Fermion Levels

52%
Wodziński D., Wójs A., Quinn J.
Acta Physica Polonica A
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2005
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vol. 108
|
issue 5
909-914
EN
Pair-distribution functions g(r) of the Laughlin quasielectrons are calculated in the fractional quantum Hall states at electron filling factorsν=4/11 and 3/8. They all have a shoulder at a medium range, supporting the idea of quasielectron cluster formation. The intra- and inter-cluster contributions to g(r) are identified. The average cluster sizes are estimated; pairs and triplets of quasielectrons are suggested atν=4/11 and 3/8, respectively.
19
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Mathematical Structure of Bosonic and Fermionic Jack States and Their Application in Fractional Quantum Hall Effect

52%
Kuśmierz B., Wu Y., Wójs A.
Acta Physica Polonica A
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2014
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vol. 126
|
issue 5
1134-1136
EN
Fractional quantum Hall effect is a remarkable behaviour of correlated electrons, observed exclusively in two dimensions, at low temperatures, and in strong magnetic fields. The most prominent fractional quantum Hall state occurs at Landau level filling factor ν = 1/3 and it is described by the famous Laughlin wave function, which (apart from the trivial Gaussian factor) is an example of Jack polynomial. Fermionic Jack polynomials also describe another pair of candidate fractional quantum Hall states: Moore-Read and Read-Rezayi states, believed to form at the ν = 1/2 and 3/5 fillings of the second Landau level, respectively. Bosonic Jacks on the other hand are candidates for certain correlated states of cold atoms. We examine here a continuous family of fermionic Jack polynomials whose special case is the Laughlin state as approximate wave functions for the 1/3 fractional quantum Hall effect.
20
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Spin Phase Transition in a Correlated Composite Fermion Liquid

52%
Wójs A., Simion G., Wodziński D., Quinn J.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
153-156
EN
We study spin polarization of the ν_e=4/11 fractional quantum Hall state corresponding to the ν=1/3 filling of the second composite fermion Landau level, and predict a spin phase transition in realistic systems.
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