共查询到20条相似文献,搜索用时 31 毫秒
1.
C. Sieh T. Meier A. Knorr F. Jahnke P. Thomas S. W. Koch 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(3):407-421
A model study of the characteristic signatures of carrier-correlation effects on the excitonic differential absorption spectra
in semiconductors is presented. Using an effectively one-dimensional tight-binding system Coulomb-induced carrier-correlations
up to third-order in the optical field are treated without additional approximations. To illustrate the influence of the different
many-body contributions excitonic differential absorption spectra are computed for various polarizations and pump-probe time
delays. The simultaneous influence of energetic disorder and correlations on the differential absorption spectra is discussed.
Also presented are numerical results for the case when the semiconductor system is placed inside a microcavity in the strong-coupling
regime. It is shown that the correlations induce characteristic signatures in the normal mode spectra.
Received 22 January 1999 相似文献
2.
V.B. Timofeev A.V. Larionov J. Zeman G. Martinez V.I. Falko M. Bayer A. Forchel 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(1):39-43
Magnetooptical studies performed on a wide InGaAs/GaAs single quantum well indicate that optically non-active (dark) excitons
with total angular momentum play the role of a reservoir for the creation of free multiparticle excitonic complexes. After analyzing the magnetic field
evolution of the circularly polarized components of the low energy structure appearing in the main excitonic luminescence
line we assign this feature to the excitonic trion formation. The binding energy of the excitonic trions was estimated to
be of the order of 1 meV.
Received: 29 October 1997 / Received in final form: 20 February 1998 / Accepted: 21 February 1998 相似文献
3.
A. Ahmad A. Alsaad 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(1):41-46
Zinc oxide thin films were sputter deposited on (100) silicon substrates at
250 ○C substrates temperature via reactive unbalanced dc magnetron
process using pure zinc target and argon/oxygen gases. The influence of the
applied dc sputtering power (between 100 to 250 Watts, step 50 Watts) on the
optical properties of the grown films was systematically investigated by
variable angle of incidence spectroscopic ellipsometry (VASE) technique. The
refractive indices were found to follow the second-order Sellmeier
dispersion relation. However, Cauchy-like dispersion model was formulated to
account for the absorption tail and excitonic structure near the direct band
gap. The optical properties such as refractive indices, extinction
coefficients, optical band gaps, Urbach's energies, excitonic binding
structure and absorption coefficients of the grown films were reported as a
function of dc power in the photon energy range between 1.2 eV and 4.2 eV.
The films were found to be polycrystalline with (002) preferred orientation. 相似文献
4.
The effect of a random field caused by impurities, interface roughness and so on, on the optical properties and superfluidity
of a quasi-two-dimensional system of excitons is studied. The influence of a random field on the density of the superfluid
component of excitonic systems at low temperatures is investigated. For quasi-two-dimensional excitonic systems in a random
field the Kosterlitz–Thouless temperature in the superfluid state is calculated. The superfluidity and Bose–Einstein condensation
of indirect excitons in coupled quantum dots are studied. Magnetoexciton light absorption in the disordered quantum wells
is considered. The two-particle problem of the magnetoexciton motion in the external field depending on the external magnetic
field is reduced to the one-particle motion with effective magnetic mass in some effective field. The energy and optical absorption
of the magnetoexciton in a single and coupled quantum dots are studied using the effective-magnetic-mass Hamiltonian. In the
coherent potential approximation the coefficient of magnetoexciton optical absorption in single and coupled quantum wells
is calculated. In the strong magnetic fields the exciton peak decreases with magnetic field increasing in accordance with
the experimental data. The localization of direct and indirect magnetoexcitons is investigated.
Received: 14 April 2000 / Accepted: 17 April 2000 / Published online: 6 September 2000 相似文献
5.
Bruneval F Vast N Reining L Izquierdo M Sirotti F Barrett N 《Physical review letters》2006,97(26):267601
State-of-the-art theoretical methods fail in describing the optical absorption spectrum, band gap, and optical onset of Cu(2)O. We have extended a recently proposed self-consistent quasiparticle approach, based on the GW approximation, to the calculation of optical spectra, including excitonic effects. The band structure compares favorably with our present angle-resolved photoemission measurements. The excitonic effects based on these realistic band structure and screening provide a reliable optical absorption spectrum, which allows for a revised interpretation of its main structures. 相似文献
6.
Wenfang Xie 《Optics Communications》2010,283(7):1381-2861
An exciton in a disc-like quantum dot (QD) with the parabolic confinement, under applied electric field, is studied within the framework of the effective-mass approximation. Both the electric field and the confinement effects on the transition energy and the oscillator strength were investigated. Based on the computed energies and wave functions, the linear, the third-order nonlinear and the total optical absorption coefficients were also calculated. We found that the optical absorption coefficients with considering excitonic effects are stronger than those without considering excitonic effects and the absorption peak will move to the right side induced by the electron-hole interaction, which shows an excitonic effect blue-shift of the resonance in QDs. The applied electric field may affect either the size or the position of absorption peaks of excitons. However, the applied electric field may only affect the size of absorption peaks of an electron-hole pair without considering excitonic effects. It is very important to take excitonic effects into account when we study the optical absorption for disc-like QDs. We may observe the excitonic effect induced by the external electric field. 相似文献
7.
We investigate the behavior of optical absorption of boron–nitride nanotubes (6,0) in the context of Hubbard model at the paramagnetic sector. GW approximation has been implemented in order to make self-energy matrix of electronic system. Afterwards, the real and imaginary parts of transverse dielectric functions have been obtained using linear response theory. The results show that the frequency gap in the optical absorption decreases with Coulomb repulsion strength. Moreover the results show that the local Coulomb interaction leads to the appearance of the excitonic effects in the optical spectrum. Finally the effects of electronic concentration on the frequency behavior of imaginary part of dielectric function have been investigated. 相似文献
8.
R. Granger J.T. Benhlal O. Ndap R. Triboulet 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(3):429-436
The dielectric function of ZnSe has been deduced from ellipsometric measurements between 20 K and 380 K. is analysed around each critical point with the standard critical point model. The variations of the different parameters
characterising each transition with temperature are presented and analysed. The temperature coefficients of the energies of
the critical transitions are given. is essentially governed by the Coulomb interaction near the fundamental gap. Thanks to the high binding energy of the exciton
and the low spectral width of the ellipsometer, the fundamental state of the exciton is found completely separated from the
first excited states and the continuum at low temperature. In return the strong transition E1 near the L points of the Brillouin zone can be described equally well with a 2D or an excitonic transition.
Received 5 February 1999 and Received in final form 15 June 1999 相似文献
9.
R. Gupta S. Biswas U.S. Ghosh C. Basu 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(4):635-640
Magnetic measurements of octahydrated Holmium sulphate have been carried out in the temperature range 80-300 K and analysis
of the results has been performed using a crystal field of symmetry which is the major point symmetry of the ion inferred from the polarized optical absorption studies. The most rigorous
approach of direct diagonalization of the Hamiltonian matrix constructed in the complete basis of states belonging to all
atomic terms of the ion has been employed. A new set of crystal field parameters some of which are widely different from that reported from optical
studies, has been evaluated for consistent interpretation of both the magnetic and optical data.
Received 4 August 1998 and Received in final form 4 February 1999 相似文献
10.
M. Dumm M. Dressel M. Nicklas P. Lunkenheimer A. Loidl M. Weiden F. Steglich B. Assmann H. Homborg P. Fulde 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(3):317-322
The magnetic susceptibility, using dc and electron spin resonance (ESR) methods, the specific heat, and the infrared properties
of the one-dimensional molecular semiconductors lithium phthalocyanine (LiPc) and the iodinated compound LiPcI have been investigated
for temperatures K. LiPc has a half-filled conduction band and is expected to be an organic metal. However, due to the strong Coulomb repulsion
the system is a one-dimensional Mott-Hubbard insulator with a Hubbard gap of 0.75 eV as inferred from optical measurements.
The localized electrons along the molecular stacks behave like a S = 1/2 antiferromagnetic spin chain. The spin susceptibility, as determined by ESR experiments, and the magnetic contribution
to the heat capacity show a Bonner-Fisher type of behavior with an exchange constant K. LiPcI is an intrinsic narrow-gap semiconductor with an optical gap of 0.43 eV. In ESR experiments it is silent, indicating
that all the unpaired electrons have been removed from the macrocycle via doping with iodine.
Received: 16 June 1998 / Accepted: 14 July 1998 相似文献
11.
G. Perna V. Capozzi 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(4):401-406
CdSe and CdS films, deposited on a sapphire substrate by means of pulsed laser ablation technique, have been investigated
by means of reflectivity and photoluminescence measurements in order to study the effect of such a transparent substrate on
the optical properties of the deposited epilayers. The reflectivity spectra at low temperature have been studied by means
of an analytical model which permits one to obtain the energies of the excitonic resonances. The photoluminescence spectra
show that our CdSe and CdS films present excitonic emission at low temperature, differently from the same films deposited
on quartz. The temperature dependence of the excitonic energy has been analysed by taking into account the contribution of
both the thermal expansion and electron-phonon interaction. The exciton linewidth has been analysed according to well known
phenomenological models.
Received 21 June 2001 and Received in final form 18 November 2001 相似文献
12.
Optical Absorption Spectra and Intraband Dynamics in Terahertz-Driven Semiconductor Superlattice 下载免费PDF全文
We have theoretically investigated the optical absorption spectrum and intraband dynamics by subjecting a superlattice to both a terahertz (THz)-frequency driving field and an optical pulse by using an excitonic basis.In the presence of a THz dc field, the satellite structures in the absorption spectra are presented. The satellite structure is a result from the THz nonlinear dynamics of Wannier-Stark ladder excitons. On the other hand, the coherent intraband polarization is investigated. We find that the excitonic Bloch oscillation is driven by the THz field and yields an intraband polarization that continues to oscillate at times much longer than the intraband dephasing time. The temporal evolution of the slowly varying components of the intraband polarization is dependent on the THz frequency. 相似文献
13.
F. Mila Fu-Chun Zhang 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(1):7-10
One-dimensional spin 1 systems may have a rich phase diagram including Haldane gap and dimerized phases if the usually very
small biquadratic exchange becomes significant. We show that this unlikely condition may be fulfilled in electron systems
with quasi-degenerate orbitals. This mechanism may have been experimentally realized in the spin 1 chain LiVGe2O6. The implications for the exploration of the physics and quantum chemistry of spin 1 chains are discussed.
Received 4 January 2000 相似文献
14.
H.L. Liu M.A. Quijada D.B. Tanner H. Berger G. Margaritondo 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(1):47-56
We report on the ab-plane polarized reflectance of an untwinned single crystal over the frequency range from 80 to (10 meV-4 eV) at temperatures between 10 and 300 K. We find a clear anisotropy in the ab-plane optical conductivity above and below , which is very similar to that formerly published data of (M.A. Quijada et al., Z. Phys. B 94, 255 (1994)). We employ both the one-component and two-component analyses to the optical data, which suggest that the normal-state
infrared anisotropy of originates not only from the mass anisotropy, but also from the scattering rate anisotropy. Our results provide evidence
that the electronic structures within the plane are anisotropic. In the superconducting state, there is a definite ab-plane anisotropy to the far-infrared absorption. This anisotropy could be due either to anisotropy of the superconducting
gap or to anisotropy of the mid-infrared component to the conductivity. We also observe the superconducting condensate is
anisotropic: The value of the superconducting penetration depth in the a-direction is slightly smaller than that along the b-axis.
Received 16 July 1998 相似文献
15.
Excitonic level structures of LH1 and LH2 of purple photosynthetic bacteria using an analytical approach 下载免费PDF全文
The excitonic level structure of a ring-like chain of dimers is discussed analytically in order to aid the understanding of the possible spectral properties of LH1 and LH2 of purple photosynthetic bacteria. Under the approximation of dipole-dipole interaction between Bchls, the excitonic levels, bandwidths and energy gap between two Davydov subbands are expressed analytically in terms of interaction energies and configurational parameters of dipoles. Our model includes all the interactions between pigment molecules in the system. The oscillator strengths and circular dichroism (CD) for the excitonic states are also presented analytically. The simulated absorption and CD spectra of LH1 and LH2 complexes reproduce the main features of the measured results. 相似文献
16.
K. Maschke T. Meier P. Thomas S.W. Koch 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(4):599-606
The coherent dynamics of magnetoexcitons in semiconductor nanorings following pulsed optical excitation is studied. The calculated
temporal evolution of the excitonic dipole moment may be understood as a superposition of the relative motion of electrons
and holes and a global circular motion associated with the magnetic-field splitting of these states. This dynamics of the
electron-hole pairs can be generated either by local optical excitation of an ordered ring or, alternatively, by homogeneous
excitation of rings with broken rotational symmetry due to disorder or band tilting.
Received 27 September 2000 相似文献
17.
P.M. Visser G. Grynberg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(3):403-413
A probed optical lattice is modelled as a driven anharmonic oscillator with noise. For specific values of the probe intensity
and detuning, atoms are forced in bistable solutions. The friction and fluctuations that arise from laser cooling, determine
the equilibrium between these two modes of vibration. The distribution determines the absorption spectrum and the transient
emission spectrum that is emitted by the optical lattice after the probe has been switched off.
Received 23 May 2000 and Received in final form 17 August 2000 相似文献
18.
Th. Cabioc'h S. Camelio L. Henrard Ph. Lambin 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(3):535-540
Concentric-shell fullerenes, also called carbon onions, produced by carbon ion implantation into silver thin films, and subsequently
deposited on a silica substrate, were studied by optical transmission spectroscopy in the wavelength range 0.2 - 1.2 μm. In
this interval, the strongest absorption is due to the π-plasmon of sp2-like carbon. The position of the plasmon absorption band clearly evolved from 265 nm at low fluence to 230 nm at high implantation
fluences. A simulation of the optical spectra based on dielectric models of the concentric-shell fullerenes layer allowed
us to identify the first peak as due to disordered graphite and the latter to the carbon onions. The concentration of residual
graphite and the filling fraction of the carbon onions produced at high fluences could be estimated by fitting the optical
spectra with computed transmittance curves.
Received 13 July 2000 相似文献
19.
We present numerical calculation of the impact of electron-electron interaction on the behavior of density of states and optical properties of BeO, SiC and Boron-Nitride nanotubes and sheets. Hubbard model hamiltonian is applied to describe the dynamics of electrons on the lattice structure of theses compounds. The excitation spectrum of the system in the presence of local electronic interactions has been found using mean field approach. We find the band gap width in both optical absorption and density of states reduces with local Hubbard electronic interaction parameter. The absorption spectra exhibits the remarkable peaks, mainly owing to the divergence behavior of density of states and excitonic effects. Also we compare optical absorption frequency behavior of BeO, SiC and Boron-Nitride nanotubes with each other. Furthermore we investigate the optical properties of BeO and SiC sheets. A novel feature of optical conductivity of these structures is the decrease of frequency gap in the optical spectrum due to electronic interaction. 相似文献
20.
《理论物理通讯》2015,(11)
We present numerical calculation of the impact of electron-electron interaction on the behavior of density of states and optical properties of BeO,SiC and Boron-Nitride nanotubes and sheets.Hubbard model hamiltonian is applied to describe the dynamics of electrons on the lattice structure of theses compounds.The excitation spectrum of the system in the presence of local electronic interactions has been found using mean Seld approach.We find the band gap width in both optical absorption and density of states reduces with local Hubbard electronic interaction parameter.The absorption spectra exhibits the remarkable peaks,mainly owing to the divergence behavior of density of states and excitonic effects.Also we compare optical absorption frequency behavior of BeO,SiC and Boron-Nitride nanotubes with each other.Furthermore we investigate the optical properties of BeO and SiC sheets.A novel feature of optical conductivity of these structures is the decrease of frequency gap in the optical spectrum due to electronic interaction. 相似文献