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  1. 38 Acta Physica Polonica A

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  1. 11 Wójs A.

  2. 9 Potemski M.

  3. 5 Bryja L.

  4. 5 Karczewski G.

  5. 4 Gładysiewicz A.

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1
Content available remote

Time Resolved Magnetophotoluminescence of Biased GaAs/AlGaAs Double Quantum Well Structure

100%
Surowiecka K., Wysmołek A., Stępniewski R., Potemski M., Henini M.
Acta Physica Polonica A
|
2008
|
vol. 114
|
issue 5
1369-1374
EN
Time resolved photoluminescence of double quantum well structure was investigated versus electric and magnetic fields applied across the sample. The emission due to direct excitons (electron and hole are localized within the same quantum well) decays fast at the nanosecond timescale, whereas the recombination kinetics of indirect excitons is much slower and spreads over microseconds. The time evolution of indirect exciton emission is shown to be altered by application of either electric or magnetic field. This reflects the non-trivial effects of exciton localization which leads to the non-exponential decays of the indirect exciton emission.
2
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Magnetoexcitons in Semiconductor Quantum Rings with Complicated (Kane's) Dispersion Law

100%
Avetisyan A., Ghazaryan A., Djotyan A., Kirakosyan A., Moulopoulos K.
Acta Physica Polonica A
|
2009
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vol. 116
|
issue 5
826-828
EN
The influence of the nonparabolicity of charge carriers dispersion law (Kane's dispersion) on a magnetoexciton energy spectrum in InSb quantum rings is theoretically investigated. The analytical expression for the energy spectrum of exciton in a narrow-gap semiconductor nanoring in a magnetic field is obtained. The Aharonov-Bohm oscillations in the energy of excited states are studied.
3
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Band Mixing Effects in Quantum Well Magnetoexcitons

100%
Wysocki R., Bardyszewski W., Schoser S., Potemski M.
Acta Physica Polonica A
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1997
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vol. 92
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issue 5
1067-1071
EN
The influence of intersubband mixing in quantum wells of semiconductors with zinc-blende structure is studied both experimentally and theoretically. A multiband magnetoexciton model is described which takes into account k∙p mixing between valence subbands and the effective Coulomb interaction for an arbitrary confinement potential shape. Theoretical results reproduce very well the photoluminescence excitation spectra of GaAs/AlGaAs single quantum wells of various widths. In particular, the characteristic avoided crossing between the lowest light-hole exciton Landau level and excited heavy-hole exciton Landau level occurring at σ¯ polarization is accurately described by our theory.
4
Publication available in full text mode
Content available

Trion Binding Energies and Wave Functions in Doped Quantum Wells

100%
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.
5
Content available remote

Investigation of Spin-Glass Transition in Semimagnetic Quantum Wells Based on Cd_{1-x}Mn_{x}Te by Means of Optical Spectroscopy

100%
Zehnder U., Yakovlev D. R., Ossau W., Waag A., Landwehr G., Wojtowicz T., Karczewski G., Kossut J.
Acta Physica Polonica A
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1997
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vol. 92
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issue 5
1075-1078
EN
The spin-glass transition in Cd_{1-x}Mn_{x}Te epitaxial layers and bulk samples with 0.24 ≤ x ≤ 0.43 and in quantum well structures on the basis of Cd_{1-x}Mn_{x}Te were investigated by means of optical spectroscopy. Reduction of dimensionality of Cd_{1-x}Mn_{x}Te layers down to the quasi-two-dimensional case realized in Cd_{1-x}Mn_{x}Te/Cd_{1- y}Mn_{y}Te heterostructures frustrates the spin-glass formation, which is in agreement with theoretical predictions. The spin-glass formation is also frustrated in the vicinity of interfaces between semimagnetic and nonmagnetic semiconductors in CdTe/Cd_{1-x}Mn_{x}Te quantum wells.
6
Content available remote

Dimensional Dependence of Exchange Interactions at High Magnetic Fields

100%
Zehnder U., Kuhn-Heinrich B., Ossau W., Waag A., Landwehr G., Cheng H., Nicholas R.
Acta Physica Polonica A
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1996
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vol. 90
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issue 5
989-992
EN
We studied the contribution of the breaking of antiferromagnetically coupled spin clusters to the total magnetization in thin (CdMn)Te layers as a function of the layer thickness by reflectivity spectroscopy in magnetic fields up to 45 T. The experimental results show that the contribution of the breaking of antiferromagnetically coupled spin clusters is reduced by decreasing layer thickness.
7
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Time-Resolved Studies of Gallium Nitride Doped with Gadolinium

80%
Witek B., Wysmołek A., Kamińska M., Twardowski A., Potemski M., Boćkowski M., Grzegory I.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1425-1430
EN
Time-resolved photoluminescence experiments on high quality bulk GaN doped with Gd are presented. It was found that the decay time of Gd-related transitions observed for 4.2 K around 1.78 eV is of about 3 ms. Such a long decay time strongly supports the identification of this emission band as due to transitions between Gd³+(4f⁷) levels. The decay time measured for Gd-related transitions observed in the UV spectral range, close to the GaN band-gap, was found to be much faster than 1 μs. This suggests that these emission lines could hardly be correlated with internal transitions within Gd³+(4f⁷). Possible origin of the Gd-related UV luminescence is discussed.
8
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Charged Excitons in the Quantum Hall Regime

80%
Schüller C., Broocks K., Schröter P., Heyn C., Heitmann D., Bichler M., Wegscheider W., Apalkov V., Chakraborty T.
Acta Physica Polonica A
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2004
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vol. 106
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issue 3
341-353
EN
We review our recent optical experiments on two-dimensional electron systems at temperatures below 1 K and under high magnetic fields. The two-dimensional electron systems are realized in modulation-doped GaAs-AlGaAs single quantum wells. Via gate electrodes the carrier density of the two-dimensional electron systems can be tuned in a quite broad range between about 1×10^{10} cm^{-2} and 2×10^{11} cm^{-2}. In dilute two-dimensional electron systems, at very low electron densities, we observe the formation of negatively charged excitons in photoluminescence experiments. In this contribution we report about the observation of a dark triplet exciton, which is observable at temperatures below 1 K and for electron filling factors <1/3, i.e., in the fractional quantum Hall regime only. In experiments where we have increased the density of the two-dimensional electron systems so that a uniform two-dimensional electron system starts to form, we have found a strong energy anomaly of the charged excitons in the vicinity of filling factor 1/3. This anomaly was found to exist in a very narrow parameter range of the density and temperature, only. We propose a model where we assume that localized charged excitons and a uniform Laughlin liquid coexist. The localized charged exciton in close proximity to the Laughlin liquid leads to the creation of a fractionally-charged quasihole in the liquid, which can account for the experimentally observed anomaly.
9
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Content available

Photoluminescence of Charged Excitons in Fractional Quantum Hall Systems

80%
Wójs A.
Acta Physica Polonica A
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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.
10
Content available remote

Quantum Dots - Theory for Experiments

80%
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.
11
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Semiconductor Cavity Quantum Electrodynamics with Single Quantum Dots

80%
Reitzenstein S., Schneider C., Münch S., Kistner C., Strauss M., Huggenberger A., Franeck P., Weinmann P., Kamp M., Höfling S., Worschech L., Forchel A.
Acta Physica Polonica A
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2009
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vol. 116
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issue 4
445-450
EN
This paper summarizes recent progress achieved in the field of semiconductor cavity quantum electrodynamics with single quantum dots with the focus being on micropillar cavities. Light-matter interaction both in the strong and weak coupling regime is presented. Resonance tuning of the quantum dot by temperature, electric fields and magnetic fields is demonstrated while the strong coupling regime can be reached. Additionally, deterministic device integration of single positioned quantum dots is reported by a combination of site controlled quantum dot growth via directed nucleation and subsequent device alignment to overcome the degree of randomness of the quantum dot position in so far most common quantum dot-cavity systems.
12
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Comparative Numerical Analysis of Quasi-Two-Dimensional Negative and Positive Trions in High Magnetic Fields

80%
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.
13
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Exciton Trions in II-VI Heterostructures

80%
Cox R., Huard V., Kheng K., Lovisa S., Miller R., Saminadayar K., Arnoult A., Cibert J., Tatarenko S., Potemski M.
Acta Physica Polonica A
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1998
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vol. 94
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issue 2
99-109
EN
Optical spectra associated with transitions that create or annihilate charged excitons X^{-} or X^{+} can be observed in quantum well heterostructures containing an electron gas or a hole gas, respectively. A review is given of properties of trion states in CdTe quantum wells in zero field and of the magnetic field-dependence of the circular polarization and oscillator strength of the trion optical resonance. The possibility that disorder is needed to stabilise trion states in concentrated 2D electron or hole systems is discussed.
14
Publication available in full text mode
Content available

Temperature Dependence of Exciton and Trion States in CdTe Quantum Well at High Magnetic Fields

80%
Andronikov D., Platonov A., Crooker S., Barrick T., Karczewski G.
Acta Physica Polonica A
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2005
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vol. 108
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issue 4
653-660
EN
Temperature dependent photoluminescence and reflectivity spectra of excitons, singlet and triplet states of trions were studied in CdTe-based quantum wells at high magnetic fields. Interesting features of the exciton and trion spectral lines with altering temperatures are explained by analyzing the thermal population and the kinetics of the exciton-electron-trion energetic system.
15
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Optically Detected Magnetic Resonance of Excess Electrons in CdTe/(Cd,Mg)Te Quantum Wells

80%
Hu C., Ossau W., Yakovlev D., König B., Wojtowicz T., Karczewski G., Kossut J.
Acta Physica Polonica A
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1998
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vol. 94
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issue 2
351-354
EN
The spin resonance of excess electrons is observed with the detection either on the neutral or the negatively charged exciton X^{-} emission in type I CdTe/(Cd,Mg)Te quantum wells with excess electrons of low density. It is found that the electron spin-dependent and electron spin-conserving formation and recombination of X^{-} make the optical detection of the spin resonance of excess electrons feasible. For the first time, optically detected magnetic resonance is used to study fast optical transition processes in the nanosecond timescale where the microwave-induced magnetic transition rate is much lower than the optical transition rate.
16
Content available remote

Exciton Binding Energy and Oscillator Strength in a Shallow Quantum Well in an External Magnetic Field

80%
Zięba P., Piętka B., Łusakowski J., Tralle I.
Acta Physica Polonica A
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2015
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vol. 128
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issue 2
237-239
EN
We discuss the influence of an external magnetic field on the exciton energy and the exciton oscillator strength in the shallow quantum wells. We include into consideration the Coulomb attraction between electron and hole, which is rarely taken into account. We self-consistently solve the Schrödinger equation to compare the obtained results with the experimental values.
17
Content available remote

Experimental and Theoretical Studies of Free and Acceptor-Bound Positive Magneto-Trions

80%
Bryja L., Wójs A., Płochocka-Polack P., Gładysiewicz A., Misiewicz J., Potemski M.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
415-418
EN
By combination of polarization-resolved photoluminescence, transport, and realistic numerics we study energy and recombination spectra of free and acceptor-bound positive trions in a quasi-two-dimensional hole gas. The singlet-triplet crossing in the trion ground state is found at B≈12 T, and a slight reduction of all trion binding energies coincident with the formation of a Laughlin hole fluid is observed at B≈14.2 T.
18
Content available remote

Excitonic Polaritons in Transverse Magnetic Fields

80%
Loginov D., Kochereshko V., Litvinov A., Besombes L., Mariette H., Davies J., Smith L., Wolverson D.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
381-386
EN
Reflectivity spectra taken from wide quantum wells based on CdTe/CdZnTe and GaAs/AlGaAs (in which the well width is much larger than the exciton Bohr radius) were studied in magnetic fields in the plane of the well (the Voigt geometry). The energy splitting between bright and dark excitons and the redistribution of the oscillator strength from bright to dark was observed and this allowed us to determine the exciton exchange constantΔ. We found that exciton translational mass depends on the value of magnetic field. Additionally, we found that diamagnetic shift also depends on exciton wave vector. Changes in the spectra in the range of the overlap of heavy and light hole exciton resonances were observed when the magnetic field was inverted. Theoretical modeling of the spectra allowed us to explain all the observed features in the reflectivity spectra and to determine some material parameters.
19
Content available remote

Combined Exciton-Cyclotron Resonance in Photoluminescence of a Two-Dimensional Hole Gas

80%
Jadczak J., Bryja L., Płochocka P., Wójs A., Misiewicz J., Maude D., Potemski M.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
852-853
EN
A two-dimensional hole gas in an asymmetric GaAs/Ga_{1-x}Al_{x}As quantum well is studied by polarization-resolved photoluminescence in high magnetic fields (up to B = 20 T) and at low temperatures (down to T = 50 mK). In addition to the previously reported dominant emission channels of various free and acceptor-bound trions, the high-energy hole cyclotron replicas of the bound states are now also observed, corresponding to the combined exciton-cyclotron resonance. Identification of different transitions in the rich, multi-peak spectra was possible by the analysis of optical selection rules and comparison of the experimental spectra with realistic numerical calculations.
20
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Magnetooptical Properties of (Ga,Fe)N Layers

80%
Papierska J., Rousset J., Pacuski W., Kossacki P., Golnik A., Nawrocki M., Gaj J., Suffczyński J., Kowalik I., Stefanowicz W., Sawicki M., Dietl T., Navarro-Quezada A., Faina B., Li T., Bonanni A.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
921-923
EN
Magnetooptical properties of (Ga,Fe)N layers containing various concentrations of Fe-rich nanocrystals embedded in paramagnetic (Ga,Fe)N layers are reported. Previous studies of such samples demonstrated that magnetization consists of a paramagnetic contribution due to substitutional diluted Fe ions as well as of ferromagnetic and antiferromagnetic components originating from Fe-rich nanocrystals, whose relative abundance can be controlled by the growth conditions. The nanocrystals are found to broaden and to reduce the magnitude of the excitonic features. However, the ferromagnetic contribution, clearly seen in SQUID magnetometry, is not revealed by magnetic circular dichroism. Possible reasons for differences in magnetic response determined by magnetic circular dichroism and SQUID measurements are discussed.
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