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Wyświetlanie 1-15 z 67
Tytuł:
Valence Band Quantization in a Spherical Quantum Dot
Autorzy:
Buczko, R.
Powiązania:
https://bibliotekanauki.pl/articles/1923770.pdf
Data publikacji:
1992-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Dx
Opis:
An analytical solution of the effective mass equation for a spherical valence band in cubic semiconductors is presented. The full degeneracy of the valence band, i.e. the light-hole, heavy-hole and spin-orbit split-off subbands, were taken into account. The analytical wave functions of the valence band were used for its quantization in a completely isolated (infinite potential barrier approximation) quantum dot. The dependence of discrete valence levels on the dot diameter is presented for the CuCl case.
Źródło:
Acta Physica Polonica A; 1992, 82, 5; 789-792
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical Processes in Quantum Wells
Autorzy:
Sham, L. J.
Powiązania:
https://bibliotekanauki.pl/articles/1931845.pdf
Data publikacji:
1995-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Dx
78.55.Cr
Opis:
A review is given of the theoretical framework of exciton dynamics in quantum wells including the spin degrees of freedom. A study is made of various momentum, energy, and spin relaxation mechanisms including the effects of exciton-phonon interaction, the single-particle spin-flips by means of spin-orbit interaction and the exciton spin-flip by means of the exchange interaction. All these competing mechanisms are taken into account in a set of equations governing the time evolution of the exciton spin populations. Solutions are then used to interpret observed time-resolved observations of polarized luminescence spectra. For excitons in a two-dimensional system such as a semiconductor quantum well, the breaking of the translational symmetry in the direction normal to the interface plane has been shown theoretically by Hanamura, by Andreani and Bassani, and by Citrin to result in a recombination rate much faster than in a three-dimensional system. Yet, experiments show comparable decay rates in two- and three-dimensional excitons. Recent experiments with high time resolutions show two decay times for the total luminescence intensity. The slower one agrees with the one usually observed and interpreted as the radiative recombination time. We shall give an explanation for the fast decay as a combination of radiative recombination and single-particle spin-flip and for the slow decay as the radiative recombination slowed down by the presence of lower energy dark states for excitons with parallel spins. The ability to use the same theory to account for the polarization behavior confirms the importance of the exciton spin dynamics. Furthermore, the longitudinal electric field dependence is used to check our theory of exchange.
Źródło:
Acta Physica Polonica A; 1995, 87, 1; 7-15
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Solid State Quantum Interferometers (with and without the Warts)
Autorzy:
Washburn, S.
Powiązania:
https://bibliotekanauki.pl/articles/1931867.pdf
Data publikacji:
1995-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Dx
Opis:
A brief review of quantum interference in small conductors is followed by a discussion of quantum interference in ballistic conductors. The ballistic conductors are characterized by conservation of the momentum vector and this leads to a simple model for the details of the conductance of the system. In contrast, for diffusive conductors one can only predict the statistical behavior of the interference contributions to the conductance. The response of the ballistic interferometers is governed by semiclassical physics of the electron momentum states (i.e. the modes) in the quantum conductor. Under circumstances of reduced backscattering of the modes, the interference pattern appears to imitate that from a simple optical interferometer. New results from ballistic interferometers are reviewed briefly.
Źródło:
Acta Physica Polonica A; 1995, 87, 1; 57-66
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Two-Electron Quantum Dots in Magnetic Field
Autorzy:
Adamowski, J.
Spisak, B.
Powiązania:
https://bibliotekanauki.pl/articles/1968005.pdf
Data publikacji:
1997-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Dx
Opis:
A theoretical description is given for electronic properties of semiconductor quantum dots in a magnetic field. A two-electron model is applied for electrons in a cylindrical quantum dot with a parabolic confinement potential. The eigenvalue problem is solved by the variational method with the trial wave function proposed in the form of linear combination of S-type and P-type Gaussians. The energy levels of singlet and triplet states with arbitrary radial and magnetic quantum numbers have been calculated as a function of the applied magnetic field. The calculated cyclotron transition energies agree well with those measured for InGaAs/GaAs quantum dots. It is shown that the electron-electron interaction has a small influence on the transition energy.
Źródło:
Acta Physica Polonica A; 1997, 92, 4; 695-698
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ground-State Structure of a Two-Electron Quantum Dot
Autorzy:
El-Said, M.
Powiązania:
https://bibliotekanauki.pl/articles/2014017.pdf
Data publikacji:
2000-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Dx
Opis:
The energy spectrum of two interacting electrons, confined in a parabolic quantum dot, presented in a magnetic field is obtained. We have analyzed the energy level crossings between spin-singlet and spin-triplet states. The influence of the quantum dot size on these crossings is also shown. The results of our calculations seem to be in good agreement with analytical and exact numerical data.
Źródło:
Acta Physica Polonica A; 2000, 97, 6; 1023-1032
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Road to Quantum Boxes
Autorzy:
Chang, L. L.
Powiązania:
https://bibliotekanauki.pl/articles/1946514.pdf
Data publikacji:
1996-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Dx
73.61.-r
78.66.-w
Opis:
Quantum wells and superlattices have evolved over the last two decades to become a prominent multi-disciplinary field in condensed matter science. From the first observation of resonant tunneling to the recent realization of the quantum box, in this work we provide a summary description of the historical development of the field, known today as quantum structures. The focus is on the physics aspect with emphasis on important experimental observations that collectively define the field and set its direction of development.
Źródło:
Acta Physica Polonica A; 1996, 90, 4; 603-612
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Model of the Electron Transport in a Quantum Wire with Contacts
Autorzy:
Jungwirth, T.
Powiązania:
https://bibliotekanauki.pl/articles/1924221.pdf
Data publikacji:
1992-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Dx
Opis:
A new model of the electron transport in a quantum wire with contacts is presented. The contact between the reservoir and the quantum past of the system is assumed to be lengthwise the ideal lead. The equilibrium state of electrons in the reservoir gives the final distribution of a non-equilibrium electron system in the ideal lead. The model enables a continuous quasi-1D description of the electron transport evoked by a difference of chemical potentials as well as by a difference of temperatures of reservoirs.
Źródło:
Acta Physica Polonica A; 1992, 82, 5; 882-886
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theoretical Description of Shell Filling in Cylindrical Quantum Dots
Autorzy:
Szafran, B.
Bednarek, S.
Adamowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1992210.pdf
Data publikacji:
1998-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Dx
Opis:
A theoretical quantitative description is given for non-periodic oscillations observed in a current vs. gate voltage characteristics of cylindrical quantum dots. Energy eigenvalues and chemical potentials for a system of N confined electrons (N=1,...,13) are calculated by the unrestricted Hartree-Fock method with a confinement potential proportional to the gate voltage. The positions of the observed peaks of the current are reproduced with a very good accuracy. The non-periodicity of the characteristic is explained as a result of the shell filling, which is a signature of the quantum Coulomb blockade.
Źródło:
Acta Physica Polonica A; 1998, 94, 3; 555-559
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stark Effect for Donors in Double Quantum Wells
Autorzy:
Rolnik, S.
Adamowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1933967.pdf
Data publikacji:
1995-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Dx
73.20.Hb
Opis:
The problem of a hydrogenic donor in a semiconductor double quantum well under a homogeneous electric field is studied by variational means. The energy levels corresponding to the quantum states 1s, 2s, 2p have been calculated with the help of the many-element variational basis consisting of the exponential functions. The influence of the electric field on the donor binding energy is determined for different impurity positions. The 1s-2p transition energies have been calculated for a possible comparison with experiment.
Źródło:
Acta Physica Polonica A; 1995, 88, 5; 893-896
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Polaron Problem in Quantum Wells
Autorzy:
Bardyszewski, W.
Prywata, M.
Powiązania:
https://bibliotekanauki.pl/articles/1934053.pdf
Data publikacji:
1995-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.Ey
71.38.+i
73.20.Dx
Opis:
The effect of polar interaction between an electron in a quantum well and bulk longitudinal optical phonons is analysed. Electron spectral density function is calculated in the lowest order cumulant approximation. The position and linewidth of the quasiparticle peak are obtained as a function of quantum well width and temperature.
Źródło:
Acta Physica Polonica A; 1995, 88, 5; 969-973
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Variational Calculation for Triangular Quantum Wells Using Modified Trial Wave Function
Autorzy:
Pödör, B.
Powiązania:
https://bibliotekanauki.pl/articles/1933949.pdf
Data publikacji:
1995-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.20.Dp
73.20.Dx
Opis:
In calculations involving triangular quantum wells the Fang-Howard variational wave function is widely used because of its simplicity, although it can lead to substantial errors. This can also occur in transport calculations, where the scattering rate, being proportional to the integral of the fourth power of the wave function, depends strongly on the shape of the wave function. A new set of one-parameter wave functions is introduced and the relaxation time is evaluated for short range scatterers. The improved wave function leads up to about 22 per cent increase in the scattering rate, and to a comparable decrease in the relaxation time.
Źródło:
Acta Physica Polonica A; 1995, 88, 5; 869-872
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Acceptor in Quantum Dot in Cubic Semiconductors
Autorzy:
Janiszewski, P.
Suffczyński, M.
Powiązania:
https://bibliotekanauki.pl/articles/1943960.pdf
Data publikacji:
1995-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.66.Fd
73.61.Ey
73.20.Dx
Opis:
Energy levels and oscillator strengths for transitions between the lowest states of an acceptor in a quantum dot of finite potential barrier in cubic semiconductors have been computed in the effective-mass approximation. The degeneracy of the valence band in cubic semiconductors was taken into account in the spherical approximation. Variational envelope functions consisted of a finite basis of exponentials, and had to satisfy appropriate boundary conditions to ensure the hermiticity of the Hamiltonian matrix. In typical cubic semiconductors we have found enhanced values, by an order of magnitude, of oscillator strengths for the acceptor optical transitions in the dots of radii comparable to the acceptor diameter.
Źródło:
Acta Physica Polonica A; 1995, 88, 6; 1171-1177
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phonon Confinement and Electron Capture Time in Quantum Well
Autorzy:
Kálna, K.
Powiązania:
https://bibliotekanauki.pl/articles/1968118.pdf
Data publikacji:
1997-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.15.Nj
73.61.Ey
73.20.Dx
Opis:
The electron capture time via an electron-polar optical phonon interaction is calculated considering the confinement of a phonon in a GaAs quantum well laser structure. The effect of the phonon confinement decreases the electron capture time about twice comparing the electron capture time obtained from the interaction of an electron with the bulk phonon.
Źródło:
Acta Physica Polonica A; 1997, 92, 4; 805-808
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Quantum Dots - Theory for Experiments
Autorzy:
Jacak, L.
Krasnyj, J.
Wójs, A.
Powiązania:
https://bibliotekanauki.pl/articles/1967993.pdf
Data publikacji:
1997-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Dx
71.35.Ji
78.20.Ls
Opis:
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.
Źródło:
Acta Physica Polonica A; 1997, 92, 4; 633-640
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Binding Energies of Excitons in Quantum Well Structures
Autorzy:
Neugebauer, F.
Suisky, D.
Heimbrodt, W.
Powiązania:
https://bibliotekanauki.pl/articles/1992047.pdf
Data publikacji:
1998-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.35.-y
73.20.Dx
Opis:
Binding energies of excitons in quantum well structures have been studied by solving the time-dependent Schrödinger equation where the potential is made up by the confining quantum well potentials of arbitrary form and the Coulomb interaction between the electron and hole. The problem is solved without the usually assumed variational procedure and the separation ansatz for the confined electron and hole states. The wave functions for electrons and holes can be extracted from the exciton wave function and are used for the interpretation of the charge localization.
Źródło:
Acta Physica Polonica A; 1998, 94, 3; 459-462
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 67

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