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The Radiative Biexciton-exciton Recombination in Wurtzite Crystals

100%
Ungier W.
Acta Physica Polonica A
|
1998
|
vol. 94
|
issue 3
588-592
EN
In the effective mass approximation in the two-band model of semiconductor the dipole moment matrix element due to the biexciton-exciton transition is expressed by the functional of the exciton and biexciton envelopes. In comparison to previous estimations of the biexciton-exciton transition probability the detailed band structure at band extrema was taken into account and the biexciton envelope optimized by variational calculation was used in calculations. The oscillator strength ratio I^{2}=f_{biex-ex}/f_{band-to-band} is given for several values of σ=m_{e}/m_{h}. The calculated functional I for CdS is about four times smaller compared to that obtained by Hanamura. The calculated giant oscillator strength of the biexciton-exciton recombination in CdS is f_{biex-ex}=4×10^{2}.
2
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Excitonic Molecule in CuCl Crystal

100%
Ungier W.
Acta Physica Polonica A
|
1993
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vol. 83
|
issue 6
803-816
EN
The electronic structure of a biexciton is discussed while taking into account the detailed band structure of CuCl. The fine structure of the excitonic molecule is clarified with the effective electron-hole exchange effect taken into account beyond the effective mass approximation. The electron-hole exchange interaction mixes the states of opposite parities with respect to the permutation of electrons and holes. Two trial envelope functions, symmetric and antisymmetric under the permutation of two electrons or two holes, were used in the numerical minimization of the ground state energy of the biexciton. The obtained binding energy of the biexciton, as well as, the ratio of the mixing of the trial envelope functions of opposite parities are presented.
3
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The Nonlinear Absorption Coefficient for Direct Two-Photon Creation of Biexciton

63%
Ungier W., Suffczyński M.
Acta Physica Polonica A
|
2002
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vol. 101
|
issue 2
295-300
EN
The absorption coefficient for the two-photon creation of biexciton is calculated for CuCl and wurtzite crystals. Because of the resonance effect only the intermediate lowest optically active excitonic states are taken into account. The absorption coefficient is expressed by a functional of the biexciton envelope. The numerical results are computed with the envelope function of Hylleraas-Ore type (modified and minimized by Brinkman et al). The obtained results for CuCl are in good agreement with absorption measurements published by Gale and Mysyrowicz.
4
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Direct Two-Photon Creation of Excitonic Molecule in CuCl

51%
Ungier W., Janiszewski P., Suffczyński M.
Acta Physica Polonica A
|
2000
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vol. 98
|
issue 4
411-417
EN
The probability of direct excitation of excitonic molecule in the two-photon absorption process is calculated with an Hylleraas-Ore type biexciton envelope, which is variationally optimized. In the second order of perturbation, because of the resonance effect, only the exciton Γ_{5} intermediate state is taken into account. The band structure at band extrema due to spin-orbit interaction is assumed. The transition probability of two-photon absorption is expressed by matrix element between the free exciton and the biexciton envelopes. The obtained probability of two-photon absorption in CuCl is about three orders of magnitude smaller when compared to that obtained by Hanamura.
5
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Spin Resonance Absorption in a 2D Electron Gas

51%
Ungier W., Jantsch W., Wilamowski Z.
Acta Physica Polonica A
|
2007
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vol. 112
|
issue 2
345-350
EN
We analyze the power absorption at electron spin resonance excited by the Bychkov-Rashba spin-orbit field in a 2D electron gas. We show that, as long as the absorbed power is dissipated by the usual spin lattice relaxation mechanisms, the resonance line shape is expected to be of pure absorption type, i.e., it can be described by the imaginary part of the dynamic magnetic susceptibility. Therefore, the Dysonian line shape observed in ESR of 2D electron gas cannot result from this type of the resonance signal.
6
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Excitonic Molecule in Wurtzite Crystals

51%
Ungier W., Janiszewski P., Suffczyński M.
Acta Physica Polonica A
|
1994
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vol. 85
|
issue 3
607-613
EN
We calculate with the variational technique the fine structure of a biexciton in wurtzite crystals with the effective electron-hole exchange interaction taken into account. The values of the electron-hole exchange integrals are taken from the free exciton Γ_{5}-Γ_{6} splitting. We calculate the biexciton dissociation energy and the ratio of mixing of the symmetric and antisymmetric envelopes which arises from the electron-hole exchange interaction. Results are presented for CdS, CdSe and ZnS crystals.
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