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1.
Exciton absorption spectra in high-quality β-ZnP2 single crystals have been investigated at T=1.7 K for various directions of the wave vector and various polarization states of the radiation. It has been unambiguously
established that the additional high-energy A series, which in some works has been called a D series and ascribed to ZnP2 crystals, of so-called “rhombic” symmetry,1,8,10,11 is an intrinsic exciton of the β-ZnP2 series. A mixed mode has been detected for the first time, and the energy of the longitudinal exciton has been determined.
The selection rules for the exciton transitions have been analyzed by a group-theoretical approach, and the symmetry of the
nS states of the single exciton has been established on the basis of the experimental data — Γ
2
−
(z).
Fiz. Tverd. Tela (St. Petersburg) 41, 193–202 (February 1999) 相似文献
2.
R. A. Bisengaliev É. D. Batyrev B. V. Novikov A. V. Sel’kin 《Physics of the Solid State》1998,40(5):806-807
The exciton photoreflection spectra of CdS crystals are studied. It is found that the form of the exciton photoreflection
spectrum is determined by a Stark shift of the exciton energy in the electric field of surface states. The dependences of
the exciton photoreflection spectrum on temperature on the intensity and wavelength of the modulating radiation, and on the
processes by which the photoreflection signal relaxes is determined. An energy scheme is proposed for the surface states which
explains the observed effects of photoinduced changes in the surface field. A correlation is established between the exciton
photoreflection spectrum and the form of the fine structure in the photoconductivity.
Fiz. Tverd. Tela (St. Petersburg) 40, 875–876 (May 1998) 相似文献
3.
Quantitative investigations of the hydrogen-like exciton B series in the absorption spectra of the β-ZnP2 crystal for various wave vector directions and polarization states of radiation are conducted. It is shown that the B spectrum constitutes a single orthoexciton series with S-type envelope functions, and low-energy components in doublet lines belong to the S-type for lines in the series with n≥3. Polariton effects are clearly manifested at the B n=1 exciton resonance, and Bouguer’s law is violated. The oscillator strength tensor components are determined for transitions to the exciton states of the B series, and the polariton parameters at the B n=1 exciton resonance are calculated. 相似文献
4.
S. O. Romanovskii A. V. Sel’kin I. G. Stamov N. A. Feoktistov 《Physics of the Solid State》1998,40(5):814-815
A study is made of the effect of electric fields on the exciton states of β-ZnP2 crystals (T=77 K) in structures with Schottky barriers formed by depositing semitransparent electrically-conducting InSnO2 films on the crystal surface. The observed changes in the exciton optical reflection spectra when an electrical potential
is applied to a barrier are explained by the shift and broadening of the exciton level caused by the Stark effect. The experimental
data are compared with calculations based on a theory of exciton optical reflection from planar spatially nonuniform structures.
Fiz. Tverd. Tela (St. Petersburg) 40, 884–886 (May 1998) 相似文献
5.
S. A. Permogorov A. N. Reznitskii L. N. Tenishev A. V. Kornievskii S. Yu. Verbin S. V. Ivanov S. V. Sorokin W. von der Osten H. Stolz M. Jütte 《Physics of the Solid State》1998,40(5):743-744
Exciton dynamics in ZnCdSe/ZnSe quantum-well structures have been studied from luminescence spectra obtained at T=2 K. The energy and phase relaxation times of localized exciton states have been determined from a study of the destruction
of exciton optical alignment by an external magnetic field and direct measurements of the polarized-radiation decay kinetics
in the picosecond range. The exciton polarization lifetimes measured by two independent techniques are found to be in a good
agreement.
Fiz. Tverd. Tela (St. Petersburg) 40, 809–810 (May 1998) 相似文献
6.
A. I. Tartakovskii V. D. Kulakovskii Yu. I. Koval’ T. B. Borzenko A. Forchel J. P. Reithmaier 《Journal of Experimental and Theoretical Physics》1998,87(4):723-730
The structure of the photon states and dispersion of cavity polaritons in semiconductor microcavities with two-dimensional
optical confinement (photon wires), fabricated from planar Bragg structures with a quantum well in the active layer, are investigated
by measuring the angular dependence of the photoluminescence spectra. The size quantization of light due to the wavelength-commensurate
lateral dimension of the cavity causes additional photon modes to appear. The dispersion of polaritons in photon wires is
found to agree qualitatively with the prediction for wires having an ideal quantum well, for which the spectrum is formed
by pairwise interaction between exciton and photon modes of like spatial symmetry. The weak influence of the exciton symmetry-breaking
random potential in the quantum well indicates a mechanism of polariton production through light-induced collective exciton
states. This phenomenon is possible because the light wavelength is large in comparison with the exciton radius and the dephasing
time of the collective exciton state is long.
Zh. éksp. Teor. Fiz. 114, 1329–1345 (October 1998) 相似文献
7.
Optical-resonance-Raman scattering by acoustic phonons is used to study the effect of an electric field on the state of excitons
in GaAs/AlAs superlattices. When the energy of the exciting photon coincides with the energy of an exciton bound to Wannier-Stark
states of a heavy hole and electron with Δn=0,±1, the acoustic Raman scattering is enhanced. Oscillations in the intensity of the Raman spectrum in the electric field
are explained by resonance delocalization of the exciton ground state as it interacts with Wannier-Stark states of neighboring
quantum wells or with Wannier-Stark states of a higher electron miniband.
Fiz. Tverd. Tela (St. Petersburg) 40, 827–829 (May 1998) 相似文献
8.
A vibronic charge-transfer exciton, which is a pair of Jahn-Teller electron and hole polarons, is considered as a possible
cause of the appearance of the Müller phase in the virtual ferroelectric SrTiO3 and the “green” luminescence in the virtual ferroelectric KTaO3. The two “green” luminescence bands can be associated with emission from two states of a typical intrinsic defect, viz.,
a vibronic charge-transfer exciton trapped by an oxygen vacancy and an isolated vibronic charge-transfer exciton. In both
cases the “green” luminescence corresponds to the recombination of the electron and the hole in the vibronic charge-transfer
exciton, which is accompanied by the emission of light. The properties of the Müller phase can be attributed to mixing of
the normal state and states of the vibronic charge-transfer exciton phase when they interact with polarization in the soft
SrTiO3 matrix under the conditions of a pseudo-Jahn-Teller (pseudo-JT) effect on a soft TO mode of the displacement type. In this
case the vibronic charge-transfer exciton phase forming the low-lying excited states has “order-disorder” degrees of freedom
and exists at temperatures significantly below the point of the order-disorder ferroelectric transition in SrTiO3 at T=T
Q≈37 K. The corresponding lowering of the symmetry of the vibronic charge-transfer exciton phase to polar symmetry leads to
the possibility of a long-period incommensurate phase in such excited states, which arises as a result of the appearance of
a Lifshitz invariant. The valence-band state making the largest contribution of the pseudo-JT effect corresponds to a wave
vector equal to the critical wave vector of the incommensurate vibronic charge-transfer exciton phase. When the temperature
is lowered, the pseudo-JT distortion increases down to ∼T
Q and subsequently saturates in accordance with the saturation of the dielectric constant. The basic assumption in the model
is that the temperature T=T
Q corresponds to the narrow temperature range for the transition from an intermediate to a strong pseudo-JT effect under the
conditions for the realization of polarization tunneling states. The appearance of a significant admixture of states of the
modulated ferroelectric vibronic charge-transfer exciton phase to the ground state under the conditions for the realization
of polarization tunneling states at low temperatures provides an explanation for the principal properties of the Müller phase.
Fiz. Tverd. Tela (St. Petersburg) 40, 907–909 (May 1998) 相似文献
9.
We investigated excitons bound to shallow acceptors in high-purity ZnTe and measured excitation spectra of two-hole luminescence lines at 1.6 K using a tunable dye-laser. The electron-hole coupling in the bound exciton (BE) states appears to be very different for the various acceptors even for almost identical exciton localisation energies. Three different types of BE are reported. For the Li-acceptor BE we observe three sub-components separated by 0.22 and 0.17 meV and interpreted as J = , , states. The Ag-acceptor BE exhibits a strong ground state and a weak excited state at 1.3 meV higher energy. For the as yet unidentified k-acceptor we observe a single BE level, degenerate with the Ag-acceptor BE ground state. Dips in the excitation spectra due to absorption into free exciton 1S, 2S, and 3S states yield an exciton Rydberg R0 = 12.8±0.3 meV and a free exciton binding energy FE(1S) = 13.2±0.3 meV. 相似文献
10.
A. V. Akimov E. S. Moskalenko A. L. Zhmodikov D. A. Mazurenko A. A. Kaplyanskii L. J. Challis T. S. Cheng C. T. Foxon 《Physics of the Solid State》1997,39(4):649-653
We report the first studies of exciton luminescence spectra from asymmetric double quantum wells (DQWs) of very similar width.
The DQWs were of GaAs/AlGaAs and the differences in widths of the coupled wells were one or two monolayers. The coupled direct
and indirect exciton states anticross with a resonance splitting of 1.33 meV. An additional luminescence line appearing at
low temperatures is identified as a localized indirect exciton.
Fiz. Tverd. Tela (St. Petersburg) 39, 735–739 (April 1997) 相似文献
11.
V. A. Kosobukin 《Physics of the Solid State》1999,41(2):296-301
A theory is formulated for the elastic scattering of light through quasi-two-dimensional exciton states in a quantum well
with randomly uneven walls. The nonlocal exciton susceptibility is expressed in terms of random functions describing the shape
of the quantum well boundaries up to and including linear terms in the unevenness height. The resonance elastic scattering
cross sections in the presence of arbitrary statistical unevenness are calculated in the Born approximation for all channels
in which the initial and final states are represented by an electromagnetic TM or TE mode. The spectral and angular dependences
of the scattering probability are calculated with the unevenness characterized by Gaussian correlation functions. It follows
from numerical estimates that elastic scattering in quantum wells should be observed for unevenness having an rms height of
the order of the thickness of an atomic monolayer.
Fiz. Tverd. Tela (St. Petersburg) 41, 330–336 (February 1999) 相似文献
12.
S. V. Gupalov E. L. Ivchenko A. V. Kavokin 《Journal of Experimental and Theoretical Physics》1998,86(2):388-394
A theory is constructed for the long-range exchange and retarding interactions between an electron and a hole in a quantum
well. A method is developed that makes it possible to calculate the ground and excited states of an exciton localized as a
whole on a width fluctuation of a quantum well in the form of a rectangular island. It is shown that taking into account the
electron-hole interaction mechanisms considered here causes the radiation doublet of the exciton to split into two components
polarized along the sides of the rectangle. The dependence of the magnitude and sign of this splitting on the linear dimensions
of the island and the level number of the localized exciton are analyzed.
Zh. éksp. Teor. Fiz. 113, 703–714 (February 1998) 相似文献
13.
V. A. Morozova V. S. Vavilov O. G. Koshelev M. V. Chukichev S. F. Marenkin 《Physics of the Solid State》1998,40(5):808-809
A structure corresponding to the n=1, 2, and 3 free-exciton states is observed in the optical transmission spectra of zinc diarsenide at 5 K. The band gap for
E⊥C at temperatures of 5–300 K and the exciton binding energy (17.5 eV) are determined.
Fiz. Tverd. Tela (St. Petersburg) 40, 877–878 (May 1998) 相似文献
14.
A. A. Klochikhin 《Physics of the Solid State》1998,40(5):819-820
A unified method is developed for describing the steady-state luminescence of exciton fluctuation states for weak excitation
in different disordered systems. The phononless luminescence band is found to be formed by “radiative” states of the fluctuation
tail in the density of states, i.e., by states for which nonradiative states are either nonexistent or have a low probability.
The shape of the emission spectra calculated including the phonon interaction is in good agreement with experimental luminescence
spectra of α Si:H and of solid solutions of ZnSe(1−c)Tec and CdS(1−c)Sec.
Fiz. Tverd. Tela (St. Petersburg) 40, 890–891 (May 1998) 相似文献
15.
V. B. Timofeev A. I. Tartakovskii A. I. Filin D. Birkedal J. Hvam 《Physics of the Solid State》1998,40(5):767-769
Luminescence and luminescence excitation spectra are used to study the energy spectrum and binding energies of direct and
spatially indirect excitons in GaAs/AlGaAs superlattices having different electron and hole miniband widths in high magnetic
fields perpendicular to the heterolayers. The ground state of the indirect excitons formed by electrons and holes which are
spatially distributed among neighboring quantum wells is found to lie between the ground 1s state of the direct excitons and the threshold of the continuum of dissociated exciton states in the minibands. The indirect
excitons have a substantial oscillator strength when the binding energy of the exciton exceeds the scale of the width of the
resulting miniband. It is shown that a high magnetic field shifts a system of symmetrically bound quantum wells toward weaker
bonding. At high exciton concentrations, spatially indirect excitons are converted into direct excitons through exciton-exciton
collisions.
Fiz. Tverd. Tela (St. Petersburg) 40, 833–836 (May 1998) 相似文献
16.
17.
M. Tadi V. Mlinar F.M. Peeters 《Physica E: Low-dimensional Systems and Nanostructures》2005,26(1-4):212
Exciton states in self-assembled InP/In0.49Ga0.51P quantum dots subject to magnetic fields up to 50 T are calculated. Strain and band mixing are explicitly taken into account in the single-particle models of the electronic structure, while an exact diagonalization approach is adopted to compute the exciton states. Reasonably good agreement with magneto-photoluminescence measurements on InP self-assembled quantum dots is found. As a result of the polarization and angular momentum sensitive selection rules, the exciton ground state is dark. For in-plane polarized light, the magnetic field barely affects the exciton spatial localization, and consequently the exciton oscillator strength for recombination increases only slightly with increasing field. For z polarized light, a sharp increase of the oscillator strength beyond 30 T is found which is attributed to the enhanced s character of the relevant portion of the exciton wave function. 相似文献
18.
A. L. Yablonskii A. B. Dzyubenko S. G. Tikhodeev L. V. Kulik V. D. Kulakovskii 《JETP Letters》1996,64(1):51-56
Magnetoexcitons in InGaAs/GaAs surface quantum wells in a quantizing magnetic field are investigated theoretically and experimentally.
Dielectric enhancement of an exciton with decreasing thickness of the barrier layer is demonstrated, and the dependence of
the effect on the strength of the magnetic field is analyzed for the 1s and 2s states.
Pis'ma Zh. éksp. Teor. Fiz. 64, No. 1, 47–51 (10 July 1996) 相似文献
19.
Excitation spectra near the indirect exciton edge of AgBr at 1.8K are reported for several luminescence lines from weakly localized excitons. Excitation below the exciton absorption threshold reveals several excited bound exciton states the energetic positions of which are determined. For excitation above the threshold, strong energy dependent structure is observed. It is interpreted in terms of resonant trapping of free excitons in both ground and excited bound exciton states associated with emission of LO(Γ), long wavelength acoustic and intervalley TA(X) and LA(X) phonons as well as combinations and overtones of these. From measurements in doped crystals two bound exciton systems are found to be correlated with Cd2+ and Ca2+, respectively. 相似文献
20.
A transformation of the dimensionality of excitonic states from 2D to 3D with increasing external electric field is observed
in single GaAs/AlxGa1−x
As quantum-well structures with asymmetric barriers. The binding energy of a 2D exciton remains constant over a wide range
of variation of the field, since the decrease in the binding energy is compensated by increasingly larger penetration of the
electronic wave function into the barrier layer, where the exciton binding energy is higher because the effective mass is
larger and the dielectric constant of AlGaAs is lower than that of GaAs. When the maximum of the electron wave function is
displaced into the barrier as the field increases, the exciton binding energy decreases. As the field increases further, a
2D exciton transforms into a quasi-3D exciton, with a heavy hole in the quantum well and an electron in a resonant above-barrier
state.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 3, 207–211 (10 February 1998) 相似文献