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1.
A theory for the linear and quadratic responses of a 2D gas of indirect dipolar excitons to an external surface acoustic wave perturbation in the presence of a static random potential is considered. The theory is constructed both for high temperatures, definitely greater than the exciton gas condensation temperature, and at zero temperature by taking into account the Bose–Einstein condensation effects. The particle Green functions, the density–density correlation function, and the quadratic response function are calculated by the “cross” diagram technique. The results obtained are used to calculate the absorption of Rayleigh surface waves and the acoustic exciton gas drag by a Rayleigh wave. The damping of Bogoliubov excitations in an exciton condensate due to theirs scattering by a random potential has also been determined. 相似文献
2.
The effect of electric field on exciton states and optical properties in zinc-blende (ZB) InGaN/GaN quantum dot (QD) are investigated theoretically in the framework of effective-mass envelop function theory. Numerical results show that the electric field leads to a remarkable reduction of the ground-state exciton binding energy, interband transition energy, oscillator strength and linear optical susceptibility in InGaN/GaN QD. It is also found that the electric field effects on exciton states and optical properties are much more obvious in QD with large size. Moreover, the ground-state exciton binding energy and oscillator strength are more sensitive to the variation of indium composition in InGaN/GaN QD with small indium composition. Some numerical results are in agreement with the experimental measurements. 相似文献
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A theory of the exciton spectrum of an individual complex hexagonal nanotube in an array of hexagonal quantum tubes prepared
from InP and InAs has been proposed in the framework of the effective-mass and square-potential approximations. It has been
demonstrated that the theoretically calculated exciton spectrum agrees well with the experimental emission spectrum of the
array of widely spaced hexagonal nanotubes not only in energy positions of the peaks but also in their intensity. 相似文献
6.
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
7.
A theory of the dephasing rate of quasi-2D free excitons due to acoustic phonon interaction at low exciton densities is presented. Both deformation potential and piezoelectric couplings are considered for the exciton–phonon interaction in quantum wells. Using the derived interaction Hamiltonian obtained recently by us, exciton linewidth and dephasing rate are calculated as a function of the exciton density, exciton temperature, exciton momentum and lattice temperature. 相似文献
8.
《Physics letters. A》1987,125(5):262-266
An explicit analytic solution of the Pauli master equation for the incoherent exciton motion in the infinite linear chain with a single trap is presented. The total probability to find the exciton in the chain is also calculated. 相似文献
9.
The relation between the excitonic purity and the concurrence in a system of two coupled large semiconduction quantum dots mediated by a single-mode cavity field is investigated by using linear entropy theory. The results show the difference in describing two modes of excitonic entanglement between linear entropy and concurrence. The relation between nonclassical property of cavity field and the entanglement degree of excitons is also discussed. The results show that two modes of exciton can reach maximal entanglement when the cavity exhibits an antibunching effect. 相似文献
10.
We report on the observation of a number of new lines in the photo- luminescence spectrum of Si:Li. Some of these lines are interpreted as luminescence from excited initial states of the bound exciton and bound multiexciton complexes. Thermodynamic measurements of the binding energy for one and two exciton complexes are reported. One of the bound exciton excited states is correctly positioned to be the final state for the observed decay of the two exciton complex. 相似文献
11.
Hernando J van Dijk EM Hoogenboom JP García-López JJ Reinhoudt DN Crego-Calama M García-Parajó MF van Hulst NF 《Physical review letters》2006,97(21):216403
We present a single-molecule study unraveling the effect of static disorder on the vibrational-assisted ultrafast exciton dynamics in multichromophoric systems. For every single complex, we probe the initial exciton relaxation process by an ultrafast pump-probe approach and the coupling to vibrational modes by emission spectra, while fluorescence lifetime analysis measures the amount of static disorder. Exploiting the wide range of disorder found from complex to complex, we demonstrate that static disorder accelerates the dephasing and energy relaxation rate of the exciton. 相似文献
12.
In this paper a general theory is established for surface exciton states in a molecular crystal. Starting from the bulk exciton formalism the pertubation caused by the surface is taken into account by introducing a perturbation matrix. Symmetry properties of the “surface exciton bands” are derived. 相似文献
13.
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
14.
The theory of the multiphonon and radiative recombination of a self-trapped exciton on the interface of a silicon nanocrystal in a SiO2 matrix is developed. Self-trapped excitons play a key role in the hot carrier dynamics in nanocrystals under photoexcitation. The ratio of the probabilities of the multiphonon and radiative recombination of the self-trapped exciton is estimated. The probabilities of exciton tunnel transition from the self-trapped state to a nanocrystal are calculated for nanocrystals of various sizes. The infrared range spectrum of the luminescence of the self-trapped exciton is obtained. 相似文献
15.
The third-harmonic-generation (THG) spectrum was measured for a NiBr-chain compound, which is a one-dimensional Mott insulator, in a reflection configuration. A sharp peak and a shoulder structure in the THG spectrum are attributed to three-photon resonance to an exciton and a continuum, respectively. The band-edge energy, the exciton binding energy, and the spectral weights for the exciton and the continuum were determined from comparative studies of linear absorption, THG, and electroreflectance spectra. The excitonic effect is more pronounced in the NiCl chain than in the NiBr chain. 相似文献
16.
Yang K Chen LP Cai YQ Hiraoka N Li S Zhao JF Shen DW Song HF Tian H Bai LH Chen ZH Shuai ZG Feng DL 《Physical review letters》2007,98(3):036404
Excitons in a complex organic molecular crystal were studied by inelastic x-ray scattering (IXS) for the first time. The dynamic dielectric response function is measured over a large momentum transfer region, from which an exciton dispersion of 130 meV is observed. Semiempirical quantum chemical calculations reproduce well the momentum dependence of the measured dynamic dielectric responses, and thus unambiguously indicate that the lowest Frenkel exciton is confined within a fraction of the complex molecule. Our results demonstrate that IXS is a powerful tool for studying excitons in complex organic molecular systems. Besides the energy position, the IXS spectra provide a stringent test on the validity of the theoretically calculated exciton wave functions. 相似文献
17.
S. V. Izvekov 《Physics of the Solid State》1997,39(9):1383-1388
A nonlocal dynamic coherent-potential approximation is formulated as a further development of the dynamic coherent-potential
method. The nonlocal dynamic coherent-potential approximation is an efficient method of determining the one-exciton Green’s
function in a model with the Hamiltonian in the strong-coupling approximation, where a spectrum of optical phonons is assumed,
and the exciton-phonon interaction operator is linear or quadratic in the phonon operators. A system of recursion equations
is derived, from which the coherent potential is found as a function of the energy E and the wave vector k. An analytical expression is derived for the one-exciton Green’s function in the case of narrow (in comparison with the phonon
energy) exciton bands and exciton-phonon interaction linear in the phonon operators. For broader exciton bands and more complex
exciton-phonon interaction the system of equations determining the coherent potential represents a recursion algorithm, which
can be effectively implemented by numerical means.
Fiz. Tverd. Tela (St. Petersburg) 39, 1560–1563 (September 1997) 相似文献
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A wide range of quantum systems are time-invariant and the corresponding dynamics is dictated by linear differential equations with constant coefficients.Although simple in mathematical concept,the integration of these equations is usually complicated in practice for complex systems,where both the computational time and the memory storage become limiting factors.For this reason,low-storage Runge-Kutta methods become increasingly popular for the time integration.This work suggests a series of s-stage sth-order explicit RungeKutta methods specific for autonomous linear equations,which only requires two times of the memory storage for the state vector.We also introduce a 13-stage eighth-order scheme for autonomous linear equations,which has optimized stability region and is reduced to a fifth-order method for general equations.These methods exhibit significant performance improvements over the previous general-purpose low-stage schemes.As an example,we apply the integrator to simulate the non-Markovian exciton dynamics in a 15-site linear chain consisting of perylene-bisimide derivatives. 相似文献