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1.
《Superlattices and Microstructures》1994,15(2):193
The bound states of plasmons, of phonons and of coupled plasmon-phonon modes at neutral donors in semiconductor quantum well systems have been studied here. The interaction of plasmon-phonon excitations, which are important in compound semiconductor systems, with electrons, and the coupling of plasmons with electrons have been derived in the long wave length limit of the Random Phase approximation. These interactions are used to derive expressions for the binding energies of the collective excitations to neutral donors. The dependence of the binding energy of the coupled plasmon-phonon modes on the well width of quantum wells is found to be particularly rich. The present results are in generally good accord with available experimental data for quantum well systems. 相似文献
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G. Bastard 《Journal of luminescence》1985,30(1-4):488-501
Recent theoretical works on Coulombic bound states in semiconductor quantum wells (Q.W.) are reviewed. Due to carrier confinement along the growth axis the bound impurity or exciton states display enhanced binding energies over the bulk values. The presence of free carriers in modulation-doped quantum wells decreases the impurity binding energies. However the quasi-bidimensionality of the carrier motion prevents a complete vanishing of impurity bound states. The photoluminescence line of high-quality quantum well is often Stokes-shifted with respect to the absorption or excitation spectra. This Stokes shift can be correlated with interface defects in a qualitative fashion. 相似文献
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Polariton states have been investigated in a microcavity, where the energy of the Frenkel exciton in an organic quantum well and the energy of the semiconductor Wannier–Mott exciton in an inorganic quantum well are close to the microcavity optical mode. It has been shown that the interaction of each of these excitons with the microcavity optical mode leads to their interaction with each other and to the formation of mutually coupled hybrid excitations. The influence of the location of the quantum wells in a microcavity on the spectra of hybrid states with different polarizations has been analyzed. 相似文献
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We investigate how quantum bound states bounce from a hard surface. Our analysis has applications to ab initio calculations of nuclear structure and elastic deformation, energy levels of excitons in semiconductor quantum dots and wells,
and cold atomic few-body systems on optical lattices with sharp boundaries. We develop the general theory of elastic reflection
for a composite body from a hard wall. On the numerical side we present ab initio calculations for the compression of alpha particles and universal results for two-body states. On the analytical side we
derive a universal effective potential that gives the reflection scattering length for shallow two-body states. 相似文献
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The quantum spin Hall (QSH) state is a topologically nontrivial state of quantum matter which preserves time-reversal symmetry; it has an energy gap in the bulk, but topologically robust gapless states at the edge. Recently, this novel effect has been predicted and observed in HgTe quantum wells and in this Letter we predict a similar effect arising in Type-II semiconductor quantum wells made from InAs/GaSb/AlSb. The quantum well exhibits an "inverted" phase similar to HgTe/CdTe quantum wells, which is a QSH state when the Fermi level lies inside the gap. Due to the asymmetric structure of this quantum well, the effects of inversion symmetry breaking are essential. Remarkably, the topological quantum phase transition between the conventional insulating state and the quantum spin Hall state can be continuously tuned by the gate voltage, enabling quantitative investigation of this novel phase transition. 相似文献
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研究了抛物量子点中弱耦合束缚极化子的性质,采用改进的线性组合算符和幺正变换方法导出了束缚极化子的振动频率、有效质量和相互作用能。讨论了量子点的有效受限长度、电子LO声子耦合强度和库仑场对抛物量子点中弱耦合极化子的振动频率、有效质量和相互作用能的影响。数值计算结果表明:弱耦合束缚极化子的振动频率和相互作用能随有效受限长度的减少而急剧增大,振动频率随库仑势以及电子LO声子耦合强度的增加而增加,而相互作用能随库仑势以及电子LO声子耦合强度的增加而减小。有效质量仅与电子LO声子耦合强度有关。 相似文献
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We investigate the inter-well coupling of multiple graphene quantum well structures consisting of graphene superlattices with different periodic potentials. The general form of the eigenlevel equation for the bound states of the quantum well is expressed in terms of the transfer matrix elements. It is found that the electronic transmission exhibits resonant tunneling peaks at the eigenlevels of the bound states and shifts to the higher energy with increasing the incident angle. If there are N coupled quantum wells, the resonant modes have N-fold splitting. The peaks of resonant tunneling can be controlled by modulating the graphene barriers. 相似文献
9.
The energy spectrum of a new-type quantumwell composed of gapless graphenes with identical work functions and different Fermi velocities is investigated. Symmetric and asymmetric quantum wells are considered. In a symmetric well, there is always at least one bound state. In an asymmetric well, a bound state appears, beginning at a certain finite momentum. A possibility of appearance of boundary states is investigated. 相似文献
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Bound states of electrons (holes) in quantum wells and wires with asymmetric barriers can exist in bounded regions of two-and
one-dimensional momentum space, respectively. As the corresponding momentum increases, both the disappearance (increase of
dimensionality) and appearance (decrease of dimensionality) of bound states as well as the existence of a sequence of several
such transformations of dimensionality are possible. In the case of anisotropic effective masses in the quantum wells and
barriers, the forms of the lines of disappearance and appearance of bound states are different from the forms of the isoenergy
lines. Therefore there is a finite energy interval (i.e., electron density interval) where bound states exist on only a part
of an isoenergy line. The dimensionality of the states can be controlled with an electric field; this should be observable
in a number of the experiments discussed.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 2, 188–193 (25 January 1997) 相似文献
12.
Polaronic effects on the energy levels of a double donor impurity in quantum wells in the presence of a magnetic field 总被引:3,自引:0,他引:3
Zi-xin Liu Zhen-jiang Lai Yong-chang Huang Ya Liu Guo-jun Cheng 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(3):347-350
In the presence of a magnetic field the Hamiltonian of the single or double polaron bound to a helium-type donor impurity
in semiconductor quantum wells (QWs) are given in the case of positively charged donor center and neutral donor center. The
couplings of an electron and the impurity with various phonon modes are considered. The binding energy of the single and double
bound polaron in AlxlGa 1-xlAs/GaAs/AlxrGa 1-xrAs QWs are calculated. The results show that for a thin well the cumulative effects of the electron-phonon coupling and the
impurity-phonon coupling can contribute appreciably to the binding energy in the case of ionized donor. In the case of neutral
donor the contribution of polaronic effects are not very important, however the magnetic field significantly modifies the
binding energy of the double donor. The comparison between the binding energies in the case of the impurity placed at the
quantum well center and at the quantum well edge is also given.
Received 16 February 1999 相似文献
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本文将基于有效质量近似下的变分法,理论研究了纤锌矿InGaN/GaN staggered量子阱中的激子态和光学性质.数值结果显示了InGaN量子阱中的量子尺寸和staggered受限垒对束缚于量子阱中的激子态和光学性质有着明显的影响.当阱宽增加时,量子受限效应减弱,激子结合能降低,带间发光波长增加.另一方面,当量子阱中staggered受限势增加时,量子受限效应增强,激子结合能升高,带间发光波长降低.本文的理论结果证明了可以通过调节staggered垒高和量子尺寸来调控纤锌矿InGaN staggered量子阱中的激子态和光学性质. 相似文献
16.
本文将基于有效质量近似下的变分法,理论研究了纤锌矿InGaN/GaN staggered 量子阱中的激子态和光学性质。数值结果显示了InGaN量子阱中的量子尺寸和staggered受限垒对束缚于量子阱中的激子态和光学性质有着明显地影响。当阱宽增加时,量子受限效应减弱,激子结合能降低, 带间发光波长增加。另一方面,当量子阱中staggered受限势增加时,量子受限效应增强,激子结合能升高,带间发光波长降低。本文的理论结果证明了可以通过调节staggered垒高和量子尺寸来调控纤锌矿InGaN staggered 量子阱中的激子态和光学性质。 相似文献
17.
V. S. Krivobok S. N. Nikolaev V. S. Bagaev V. S. Lebedev E. E. Onishchenko 《JETP Letters》2014,100(5):306-310
It is predicted that superradiant states can be formed in a degenerate exciton gas in a semiconductor with an indirect fundamental absorption edge. The superradiance results from four-particle recombination processes and occurs at photon energies approximately twice as high as the band gap energy. Experimental results supporting the possibility of the observation of superradiance from SiGe/Si quantum wells are presented. 相似文献
18.
The spectra of reflection and absorption of monochromatic light by semiconductor quantum wells whose width is comparable to the wavelength of exciting radiation are calculated. The case of resonance with two closely spaced excited levels is considered. These levels can arise as a result of splitting of the electron-hole pair energy due to the magnetopolaron effect when the quantum well is placed in a strong magnetic field directed perpendicular to the plane of the quantum well. It is demonstrated that, in wide quantum wells, unlike in narrow quantum wells, the reflectance and absorptance of light depend on the quantum-well width. The theory is applicable at any reciprocal ratio of the radiative lifetime to the nonradiative lifetime of electronic excitations. 相似文献
19.
We study the angular correlation of single photons emitted from excited semiconductor quantum wells. The considered physical system is described in terms of two subsystems, the electronic part constituting the bath and the photonic part constituting the bathed subsystem, both being coupled by the light-matter interaction. From the master equations describing the coarse-grained Markovian evolution of the photonic subsystem, we derive the corresponding equations of motion for the photonic angular correlation functions. These equations are solved in the stationary, low-density limit. Experimentally, the angular correlations can be assessed by studying the interference of light emitted in different directions. In agreement with recent experimental results, we find that for ordered quantum wells angular correlations exist only in emission directions for which the projections of the photon momenta onto the plane of the quantum well are equal. This feature is a direct consequence of the Bloch character of the electronic states in an ordered quantum well. Thus the experimental study of the angular correlations of emitted photons may provide an interesting diagnostic tool to reveal the presence of disorder in semiconductor heterostructures and to characterize its influence on the electronic states near the band edges. 相似文献
20.
We study the energy spectrum of the impurity states in tunnel-coupled double quantum wells for Coulomb and short-range donor
potentials. We calculate the impurity contribution and the density of states and detect the transformation of a localized
donor state into a resonant state when the binding energy of the donor in an isolated quantum well is less than the separation
of the energy levels of the double quantum wells. In the opposite case, where the binding energy is greater than the level
separation, there is tunneling repulsion between adjacent impurity levels, with the degree of degeneracy of the levels changing
when there is tunneling mixing of the ground and excited impurity states from different wells. Resonant states emerge in an
asymmetric double quantum well, while in a symmetric double quantum well the impurity level at the barrier’s center proves
to be localized even against the background of the continuum. The calculations are based on a general expression for the impurity
contribution to the density of states in terms of a 2-by-2 matrix Green’s function, i.e., only a pair of tunnel-coupled levels
of the double quantum wells is taken into account. For an impurity with a short-range potential, we derive a matrix generalization
of the Koster-Slater solution, while the impurity with a Coulomb potential is analyzed by using the approximation of a narrow
resonance and close arrangement of the repulsive levels.
Zh. éksp. Teor. Fiz. 115, 1337–1352 (April 1999) 相似文献