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Wyświetlanie 1-15 z 25
Tytuł:
Spin-Dependent Coupling of Charged Quantum Dot Excitons with Continuum States
Autorzy:
Urbaszek, B.
Warburton, R. J.
Karrai, K.
Schulhauser, C.
Högele, A.
McGhee, E. J.
Govorov, A. O.
Gerardot, B. D.
Marie, X.
Amand, T.
Petroff, P. M.
Powiązania:
https://bibliotekanauki.pl/articles/2038350.pdf
Data publikacji:
2004-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
78.67.Hc
Opis:
Magnetic field and temperature dependent photoluminescence studies on neutral and charged excitons in individual InAs quantum dots allow us to uncover different mechanisms by which the discrete quantum dot states are coupled to delocalized continuum states in a quantum well (the wetting layer). The behaviour of the neutral and singly charged excitons can be explained taking only discrete quantum dot states into account. For doubly and triply charged excitons we have to consider spin dependent coherent and incoherent interactions between discrete quantum dot states and delocalized wetting layer states.
Źródło:
Acta Physica Polonica A; 2004, 106, 3; 395-402
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Optical Excitonic Aharonov-Bohm Effect in a Few Nanometer Wide Type-I Nanorings
Autorzy:
Tadić, M.
Arsoski, V.
Čukarić, N.
Peeters, F.
Powiązania:
https://bibliotekanauki.pl/articles/1537808.pdf
Data publikacji:
2010-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
78.67.Hc
Opis:
The optical excitonic Aharonov-Bohm effect in type-I three-dimensional (In,Ga)As/GaAs nanorings is theoretically explored. The single-particle states of the electron and the hole are extracted from the effective mass theory in the presence of inhomogeneous strain, and an exact numerical diagonalization approach is used to compute the exciton states and the oscillator strength $f_{x}$ for exciton recombination. We studied both the large lithographically-defined and small self-assembled rings. Only in smaller self-assembled nanorings we found optical excitonic Aharonov-Bohm effect. Those oscillations are established by anticrossings between the optically active exciton states with zero orbital momentum. In lithographically defined rings, whose average radius is 33 nm, $f_{x}$ shows no oscillations, whereas in the smaller self-assembled nanoring with average radius of 11.5 nm oscillations in $f_{x}$ for the ground exciton state are found as function of the magnetic field that is superposed on a linear dependence. These oscillations are smeared out at finite temperature, thus photoluminescence intensity exhibits step-like variation with magnetic field even at temperature as small as 4.2 K.
Źródło:
Acta Physica Polonica A; 2010, 117, 6; 974-977
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Interband Optical Properties of Concentric Type-I Nanorings in a Normal Magnetic Field
Autorzy:
Arsoski, V.
Tadić, M.
Peeters, F.
Powiązania:
https://bibliotekanauki.pl/articles/1537829.pdf
Data publikacji:
2010-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
78.67.Hc
Opis:
Two concentric two-dimensional GaAs/(Al,Ga)As nanorings in a normal magnetic field are theoretically studied. The single-band effective mass approximation is adopted for both the electron and the hole states, and the analytical solutions are given. We find that the electronic single particle states are arranged in pairs, which exhibit anticrossings and the orbital momentum transitions in the energy spectrum when magnetic field increases. Their period is essentially determined by the radius of the outer ring. The oscillator strength for interband transitions is strongly reduced close to each anticrossing. We show that an optical excitonic Aharonov-Bohm effect may occur in concentric nanorings.
Źródło:
Acta Physica Polonica A; 2010, 117, 5; 733-737
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Carrier Trapping in a Quantum Dash: Optical Signatures
Autorzy:
Kaczmarkiewicz, P.
Machnikowski, P.
Kuhn, T.
Powiązania:
https://bibliotekanauki.pl/articles/1403618.pdf
Data publikacji:
2012-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
73.21.La
Opis:
We theoretically study the optical properties and the electronic structure of highly elongated quantum dots (quantum dashes) and show how geometrical fluctuations affect the excitonic spectrum of the system. The dependence of the absorption intensities on the geometrical properties (depth and length) of the trapping center in a quantum dash is analyzed and the dependence of the degree of the linear polarization on these geometrical parameters is studied.
Źródło:
Acta Physica Polonica A; 2012, 122, 6; 997-1000
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nano-Optics on Individual Quantum Objects - From Single to Coupled Semiconductor Quantum Dots
Autorzy:
Bacher, G.
Schömig, H.
Welsch, M. K.
Scheibner, M.
Seufert, J.
Obert, M.
Forchel, A.
Maksimov, A. A.
Zaitsev, S.
Kulakovskii, V. D.
Powiązania:
https://bibliotekanauki.pl/articles/2035563.pdf
Data publikacji:
2002
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
75.50.Pp
73.21.La
Opis:
Some recent highlights of our optical studies on single and coupled semiconductor quantum dots are reviewed. In the first part, we concentrate on the role of spins and spin-spin interaction in nonmagnetic and magnetic single quantum dots. In the case of strictly resonant excitation of the ground state in self-assembled CdSe/ZnSe quantum dots, we find an exciton spin relaxation time, which exceeds the recombination lifetime significantly. Linear polarization has to be used for these experiments, as the electron-hole exchange interaction lifts the spin degeneracy and the eigenstates are linear combinations of spin-up and spin-down excitons. In a magnetic quantum dot, the exchange interaction between carrier spins and the spins of magnetic ions is shown to be responsible for giant magneto-optical effects. We demonstrate the formation of zero-dimensional magnetic polarons and we succeeded in measuring the magnetization on a scale of a few nanometers using the characteristic photoluminescence signal of individual quantum dots as experimental monitor. The second part is devoted to pairs of single quantum dots. On one hand, single exciton tunneling within an individual quantum dot pair is demonstrated studying single pairs of vertically correlated strain-induced and self-organized quantum dots. On the other hand, we show that in a pair of lithographically defined single dots with strongly different g-factors the energy spacing between the dot ground states can be tuned in an external magnetic field by about 10 meV, giving access to a controlled coupling between two individual quantum dots.
Źródło:
Acta Physica Polonica A; 2002, 102, 4-5; 475-494
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Oscillator Strengths of Quantum Transitions in Spherical Quantum Dot $GaAs$/$Al_{x}Ga_{1-x}As$/$GaAs$/$Al_{x}Ga_{1-x}As$ with On-Center Donor Impurity
Autorzy:
Holovatsky, V.
Bernik, I.
Voitsekhivska, O.
Powiązania:
https://bibliotekanauki.pl/articles/1207322.pdf
Data publikacji:
2014-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
78.67.Hc
71.55.-i
Opis:
The investigation of the electron and hole energies and probability densities is performed for the cases with and without the donor hydrogenic impurity placed into the centre of quantum dot quantum well structures with different thicknesses of layers. The oscillator strengths of intra- and interband quantum transitions in $GaAs$/$Al_{x}Ga_{1-x}As$ core/shell/well/shell spherical quantum dot with ionized on-center donor impurity are estimated. The oscillator strengths of quantum transitions non-monotonously depend on the width of the layers due to the different location of carriers. The optimal geometrical parameters of the nanostructure are estimated for the possibility of multicolor light emission based on interband quantum transitions.
Źródło:
Acta Physica Polonica A; 2014, 125, 1; 93-97
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Novel Multichannel Single Photon Correlations Technique Applied for the Spin Dynamics Study of a Few Mn^{2+} Ions in a CdTe/ZnTe Quantum Dot
Autorzy:
Malinowski, F.
Koperski, M.
Goryca, M.
Smoleński, T.
Golnik, A.
Kossacki, P.
Wojnar, P.
Powiązania:
https://bibliotekanauki.pl/articles/1399084.pdf
Data publikacji:
2013-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
72.21.La
75.75.-c
Opis:
In this work we demonstrate a novel experimental approach to the study of single photon correlations. The introduction of the multichannel detection setup enables the simultaneous measurement of a large number of correlation functions for photons emitted from different energetic ranges. The advantages of this new approach were exploited in a detailed study of the biexciton-exciton recombination cascade in CdTe/ZnTe quantum dots doped with a few $Mn^{2+}$ ions. The information about the dynamics of the magnetic system in the quantum dot during the lifetime of the exciton was obtained from the analysis of the correlation functions.
Źródło:
Acta Physica Polonica A; 2013, 124, 5; 791-794
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Neutral and Charged Excitons Localized in the InAs/GaAs Wetting Layer
Autorzy:
Babiński, A.
Czyż, M.
Golnik, A.
Borysiuk, J.
Kret, S.
Raymond, S.
Lapointe, J.
Wasilewski, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1811914.pdf
Data publikacji:
2008-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
78.55.Cr
78.67.Hc
Opis:
It has recently been shown that potential fluctuations in a wetting layer, which accompanies InAs/GaAs quantum dots can localize excitons. Neutral excitons and biexcitons and charged excitons were identified. In this communication we report on studies of properties of the excitons over wide temperature range (T < 70 K). The micro-photoluminescence measurements enable investigation of excitons localized in a single potential fluctuation. Temperature-induced broadening of the neutral exciton as well as a quenching of the charged exciton at temperatures higher than 50 K are observed and discussed.
Źródło:
Acta Physica Polonica A; 2008, 114, 5; 1055-1060
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Femtosecond Spectral Hole Burning Spectroscopy as a Probe of Exciton Dynamics in Quantum Dots
Autorzy:
Műller, T.
Moldaschl, T.
Parz, W.
Golka, S.
Strasser, G.
Unterrainer, K.
Powiązania:
https://bibliotekanauki.pl/articles/1813185.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
78.47.-p
78.67.Hc
Opis:
We present measurements of the dynamics of photoexcited excitons in an ensemble of InAs/GaAs self-assembled quantum dots using a femtosecond spectral hole burning technique. We use this technique to examine the exciton spin relaxation and the line shape of optical transitions in the dots.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 777-782
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Light Emission from CdS Quantum Dots Stabilized by Sugars
Autorzy:
Sergiel, I.
Mirończyk, A.
Kozioł, J.
Defort, A.
Powiązania:
https://bibliotekanauki.pl/articles/1807562.pdf
Data publikacji:
2009-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
78.67.Hc
78.55.Et
Opis:
CdS nanoparticles were successfully synthesized using starch, amylopectin and maltodextrin, as a capping agent. Optical properties of the final products have been investigated by photoluminescence spectroscopy and Raman scattering. The atomic force microscopy gave a particle of an average size of approximately 6 nm. Our research reveals that all prepared sugar-quantum dot aqueous solutions were stable against precipitation during the time of their investigation and kept their stability for several months after it.
Źródło:
Acta Physica Polonica A; 2009, 116, S; S-166-S-168
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electronic Structure of Elongated $In_{0.3}Ga_{0.7}As//GaAs$ Quantum Dots
Autorzy:
Pieczarka, M.
Musiał, A.
Podemski, P.
Sęk, G.
Misiewicz, J.
Powiązania:
https://bibliotekanauki.pl/articles/1399091.pdf
Data publikacji:
2013-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
73.21.La
73.22.-f
Opis:
In this contribution the electronic structure of large $In_{0.3}Ga_{0.7}As//GaAs$ quantum dots is studied theoretically by means of 8 band k · p modeling. These quantum dots constitute unique physical system due to the low strain limit of the Stranski-Krastanow growth mode resulting in relatively large physical volume and elongation of the quantum dots in [1-10] direction. As a result of these critical growth conditions the electronic structure is expected to be very sensitive to the nanostructure size, shape, and composition of the quantum dot as well as the accompanying wetting layer. Another peculiarity of investigated system is the confining potential which is rather shallow and weakened in comparison to standard quantum dots. It makes them very interesting in view of both fundamental study and potential applications. To reveal physical mechanisms determining the optical properties of the investigated system, the electronic structure, mainly the number of confined states, and the wave function extension as a function of both quantum dot size and geometry have been simulated numerically and the importance of electron-hole Coulomb interactions has been evaluated.
Źródło:
Acta Physica Polonica A; 2013, 124, 5; 809-812
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Intermediate Band Formation and Intraband Absorption for Electrons in an Inhomogeneous Chain of Quantum Dots
Autorzy:
Bragar, I.
Machnikowski, P.
Powiązania:
https://bibliotekanauki.pl/articles/1492856.pdf
Data publikacji:
2011-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
78.67.Hc
78.30.Fs
Opis:
We study the electron states of a chain of non-identical, vertically stacked quantum dots. We discuss how the pseudo-band formed of the ground states confined in the quantum dots disintegrates upon increasing the inhomogeneity of the electron energies and analyze the impact of localization on the intraband absorption from the pseudo-band to extended (bulk) states. We describe also the dependence of the intraband absorption spectrum on the quantum dot size.
Źródło:
Acta Physica Polonica A; 2011, 120, 5; 862-864
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
One and Two Phonon Assisted Transitions between Exciton Spin States in a Quantum Dot
Autorzy:
Roszak, K.
Machnikowski, P.
Axt, V.
Kuhn, T.
Powiązania:
https://bibliotekanauki.pl/articles/1811982.pdf
Data publikacji:
2008-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.25.Rb
73.21.La
78.67.Hc
Opis:
Exciton spin decay is studied in a self-assembled InAs/GaAs quantum dot. The spin relaxation results from an interplay of two factors: the Bir-Pikus Hamiltonian and the short-range exchange interaction, leading to one and two phonon assisted transitions. We establish a hierarchy between the resulting transition rates and show the dominating role of transverse phonons for all the transitions.
Źródło:
Acta Physica Polonica A; 2008, 114, 5; 1329-1335
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Excitonic Magnetoabsorption of Cylindrical Quantum Disks
Autorzy:
Schillak, P.
Czajkowski, G.
Powiązania:
https://bibliotekanauki.pl/articles/1492888.pdf
Data publikacji:
2011-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
73.22.Dj
73.21.La
71.35.Ji
Opis:
We show how to compute the optical functions (the complex magnetosusceptibility, dielectric function, magnetoreflection) for semiconductor quantum disks exposed to a uniform magnetic field in the growth direction, including the excitonic effects. The method uses the microscopic calculation of nanostructure excitonic wave functions and energy levels, and the macroscopic real density matrix approach to compute the electromagnetic fields and susceptibilities. The electron-hole screened Coulomb potential is adapted and the valence band structure is taken into account in the cylindrical approximation, thus separating light- and heavy-hole motions. The confinement potentials are taken as step-like both in the z and in-plane directions. Numerical calculations have been performed for $In_{0.55}Al_{0.45}As$ (disk)/$Al_{0.35}Ga_{0.65}As$ (barrier) and InP/GaP disks and the results are in a good agreement with the available experimental data.
Źródło:
Acta Physica Polonica A; 2011, 120, 5; 888-890
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Multi-Scale Simulations of Semiconductor Nanostructures
Autorzy:
Zieliński, M.
Powiązania:
https://bibliotekanauki.pl/articles/1419515.pdf
Data publikacji:
2012-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
78.67.Hc
71.15.-m
71.15.Qe
Opis:
We demonstrate a multi-domain scheme for calculation of electronic and optical properties of semiconductor nanostructures. Three progressively smaller computational domains are used for strain simulation, single particle states calculation and computation of the Coulomb scattering matrix elements. Proposed approach offers a significant reduction of computational time and memory savings without sacrificing the accuracy of obtained spectra. We illustrate this method on the example of InAs/InP self-assembled quantum dots.
Źródło:
Acta Physica Polonica A; 2012, 122, 2; 312-315
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 25

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