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1.
Interface polarons in a realistic heterojunction potential 总被引:9,自引:0,他引:9
S.L. Ban J.E. Hasbun 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(3):453-461
The ground states of interface polarons in a realistic heterojunction potential are investigated by considering the bulk and
the interface optical phonon influence. A self-consistent heterojunction potential is used and an LLP-like method is adopted
to obtain the polaron effect. The numerical computation has been done for the Zn1-xCdxSe/ZnSe system to obtain the polaron ground state energy, self energy and effective mass parallel to the interface. A simplified
coherent potential approximation is developed to obtain the parameters of the ternary mixed crystal and the energy band offset
of the heterojunction. It is found that at small Cd concentration the bulk longitudinal optical phonons give the main contribution
for lower areal electron densities, whereas the interface phonon contribution is dominant for higher areal electron densities.
The interface polaron effect is weaker than the effect obtained by the three dimensional bulk phonon and by the two dimensional
interface phonon models.
Received 17 September 1998 相似文献
2.
Q.-H Chen Y.-H. Ren Z.-K Jiao 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(3):307-313
The general properties of one-dimensional large Fr?hlich polarons in motion are investigated with the previous extended coherent
states where two-phonon correlations are considered. As a result, the polaron energy, velocity, effective mass, and average
number of virtual phonons as a function the polaron total momentum are evaluated in a wide range of the coupling constant.
In addition, rich information about virtual phonons emitted by the electron in motion is obtained. More importantly, some
intrinsic features of 1D moving polarons are presented for the first time, which may also be suited to moving polarons in
more than one dimensions.
Received: 23 October 1997 / Revised and Accepted: 27 January 1998 相似文献
3.
Qinghu Chen Yuhang Ren Zhengkuan Jiao Kelin Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(1):59-63
The Feynman-Haken variational path integral theory is, for the first time, generalized to calculate the ground-state energy
of an electron coupled simultaneously to a Coulomb potential and to a longitudinal-optical (LO) phonon field in parabolic
quantum wires. It is shown that the polaronic correction to the ground-state energy is more sensitive to the electron-phonon
coupling constant than the Coulomb binding parameter and monotonically stronger as the effective wire radius decreases. We
apply our calculations to several semiconductor quantum wires and find that the polaronic correction can be considerably large.
Received 16 November 1998 相似文献
4.
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
5.
D. Rönnow L.F. Lastras-Martínez M. Cardona 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(1):29-35
Within the past years the optical excitations of electrons have been measured for semiconductor samples of different isotope
compositions. The isotope shift observed have been compared with calculations of the effects of electron-phonon interaction
on the electronic band structure. While qualitative agreement has been obtained, some discrepancies remain especially concerning
the E1 and transitions. We have remeasured the effect of isotope mass on the E1 and transitions of germanium with several isotopic compositions. The results, obtained by means of spectroscopic ellipsometry,
confirm that the real part of the gap self-energies induced by electron-phonon interaction is larger than found from band
structure calculations, while the imaginary part agrees with those calculations, which are based on a pseudopotential band
structure and a bond charge model for the lattice dynamics. Our results agree with predictions based on the measured temperature
dependence of the gaps. We compare our data for E1 and with results for the lowest direct (E0) and indirect (Eg) gaps. The measured values of and increase noticeably with increasing isotope mass. Similar effects have been observed in the temperature dependence of in and . A microscopic explanation for this effect is not available.
Received: 6 March 1998 / Revised: 27 April 1998 /
Accepted: 15 May 1998 相似文献
6.
O. S. Barišić S. Barišić 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(1):1-9
The translationally invariant diagrammatic quantum perturbation theory (TPT) is applied to the polaron problem on the 1D lattice,
modeled through the Holstein Hamiltonian with the phonon frequency ω0, the electron hopping t and the electron-phonon coupling constant g. The self-energy diagrams of the fourth-order in g are
calculated exactly for an intermittently added electron, in addition to the previously known second-order term. The corresponding
quadratic and quartic corrections to the polaron ground state energy become comparable at t/ω0>1 for g/ω0∼(t/ω0) 1/4 when the electron self-trapping and translation become adiabatic. The corresponding non adiabatic/adiabatic crossover occurs
while the polaron width is large, i.e. the lattice coarsening negligible. This result is extended to the range (t/ω0)1/2>g/ω0>(t/ω0)1/4>1 by considering the scaling properties of the high-order self-energy diagrams. It is shown that the polaron ground state
energy, its width and the effective mass agree with the results found traditionally from the broken symmetry side, kinematic
corrections included. The Landau self-trapping of the electron in the classic self-consistent, localized displacement potential,
the restoration of the translational symmetry by the classic translational Goldstone mode and the quantization of the polaronic
translational coordinate are thus all encompassed by a quantum theory which is translationally invariant from the outset.
This represents the first example, open to various generalizations, of the capability of TPT to hold through the adiabatic
symmetry breaking crossover. Plausible arguments are also given that TPT can describe the g/ω0>(t/ω0)1/2 regime of the small polaron with adiabatic or non-adiabatic translation, i.e., that TPT can cover the whole g/ω0, t/ω0 parameter space of the Holstein Hamiltonian. 相似文献
7.
J. Chatterjee M. Mitra A.N. Das 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):573-578
A two-site double exchange model with a single polaron is studied using a perturbation expansion based on the modified Lang-Firsov
transformation. The antiferromagnetic to ferromagnetic transition and the crossover from small to large polaron are investigated
for different values of the antiferromagnetic interaction (J) between the core spins and the hopping (t) of the itinerant electron. Effect of the external magnetic field on the small to large polaron crossover and on the polaronic
kinetic energy are studied. When the magnetic transition and the small to large polaron crossover coincide for some suitable
range of J/t, the magnetic field has very pronounced effect on the dynamics of polarons.
Received 1 June 2000 相似文献
8.
Y.H. Ren Q.H. Chen Y.B. Yu Z.A. Xu W.B. Shao Z.K. Jiao 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(4):651-656
Within the framework of the second-order Rayleigh-Schr?dinger perturbation theory, we investigate the effects of the interaction
of the electron and longitudinal-optical phonons in two-dimensional semiconductive quantum dots with respect to a general
potential. We propose a simple expression for the ground state energy, and compare it with those obtained by Landau-Pekar
strong coupling theory. It is shown both analytically and numerically that the results obtained from the second-order Rayleigh-Schr?dinger
perturbation theory could be better than those from Landau-Pekar strong coupling theory when the coupling constant is sufficiently
small. Moreover, some interesting problems, such as polarons in quasi-one-dimensional quantum wires, and quasi-zero-dimensional
asymmetric or symmetric quantum dots can be easily discussed only by taking different limits. After the numerical calculations,
we find that there exists a simple dimensional scaling and symmetry relation for the ground state polaron energy. Furthermore,
we apply our results to some weak-coupling polar semiconductors such as GaAs, CdS. It is shown that the polaronic effects
are found to be quiet appreciable if the confinement lengths and smaller than a few nanometers.
Received: 3 December 1997 / Revised: 6 July 1998 / Accepted: 17 September 1998 相似文献
9.
P. Paci C. Grimaldi L. Pietronero 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(2):235-243
The inclusion of nonadiabatic corrections to the electron-phonon interaction leads to a strong momentum dependence in the
generalized Eliashberg equations beyond Migdal's limit. For a s-wave symmetry of the order parameter, this induced momentum dependence leads to an enhancement of when small momentum transfer is dominant. Here we study how the d-wave symmetry affects the above behavior. We find that the nonadiabatic corrections depend only weakly on the symmetry of
the order parameter provided that only small momentum scatterings are allowed for the electron-phonon interaction. In this
situation, We show that also for a d-wave symmetry of the order parameter, the nonadiabatic corrections enhance . We also discuss the possible interplay and crossover between s- and d-wave depending on the material's parameters.
Received 12 May 2000 相似文献
10.
G. De Filippis V. Cataudella G. Iadonisi 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(3):339-351
A simple approach to the many-polaron problem for both weak and intermediate electron-phonon coupling and valid for densities
much smaller than those typical of metals is presented. Within the model the total energy, the collective modes and the single-particle
properties are studied and compared with the available theories. It is shown the occurrence of a charge density wave instability
in the intermediate coupling regime.
Received 13 May 1998 相似文献
11.
H. Kellay J. Rouch 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(1):121-129
In this paper we study the influence of the magneto-coupling effect between the longitudinal motion component and the transverse
Landau orbits of an electron on transmission features in single barrier structures. Within the parabolic conduction-band approach,
a modified one-dimensional effective-mass Schr?dinger equation, including the magneto-coupling effect generated from the position-dependent
effective mass of the electron, is strictly derived. Numerical calculations for single barrier structures show that the magneto-coupling
effect brings about a series of the important changes for the transmission probability, the above-barrier quasi-bound states,
and the tunneling time. Through examining the variation of the above-barrier resonant-transmission spectrum with the barrier
width and observing the well-defined Lorentzian line-shape of the above-barrier resonant peaks, we convincingly show that
the above-barrier resonant transmission in single barrier structures is delivered by the above-barrier quasibound states in
the barrier region, just as the below-barrier resonant tunneling in double barrier structures is mediated by the below-barrier
quasi-bound states in the well. Furthermore, we come to the conclusion that the magneto-coupling effect brings about not only
the splitting of the above-barrier quasi-bound levels but also the striking reduction of the level-width of the quasi-bound
states, correspondingly, the substantial increase of the density of the quasi-bound states. We suggest that magneto-coupling
effects may be observed by the measurements of the optical absorption spectrum associated with the above-barrier quasi-bound
states in the single barrier structures.
Received: 26 September 1997 / Revised: 26 November 1997 / Accepted: 15 December 1997 相似文献
12.
A. La Magna R. Pucci 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(4):421-429
In this paper we have introduced a variational approach to investigate the ground state of a model which includes both the
Holstein electron-phonon interaction and the extended Hubbard electron-electron interaction. We have considered a variational
state for the phonon subsystem which generalizes the previous used forms. This state allows to take into account the possibility
of extended phonon mediated correlations. The effective electron Hamiltonian, which we have obtained, includes first and second
neighbor electron-electron interaction terms. We have treated exactly, through a Lanczos method, this effective model in the
one-dimensional case. We have applied our method to two Bechgaard salts and in these cases we have estimated the correlation
parameters. We have shown that the introduction of electron-phonon interaction allows an estimate of the on site U and nearest-neighbor V Coulomb repulsion, which are in agreement with the experimental optical spectra of the above mentioned two compounds.
Received: 30 October 1997 / Revised: 28 January 1998 / Accepted: 10 April 1998 相似文献
13.
Zu Wei Yan Xi Xia Liang 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(3):531-538
A variational theory is proposed to study the surface states of electrons in a semi-infinite ternary mixed crystal, by taking
the effect of electron-surface optical (SO) phonon interaction into account. The energy and the wave function of the electronic
surface-states are calculated. The numerical results of the energies of the surface states of the polarons and the self-trapping
energies are obtained as functions of the composition x and surface potential V0 for several ternary mixed crystal materials. The results show that the electron-phonon interaction lowers the surface-state
levels with the energies from several to scores of meV. It is also found that the self-trapping energy of the surface polaron
has a minimum at some middle value of the composition x. It is indicated that the electron-phonon coupling effect can not be neglected.
Received 4 January 1999 and Received in final form 7 January 2000 相似文献
14.
N. Vandewalle M. Ausloos 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(2):257-261
The resonance splitting in finite semiconductor superlattices which consist of a number of electric barriers is investigated.
It is found that (n-1)-fold splitting for n-barrier tunneling obtained in periodic superlattices of identical barriers no longer holds for superlattices which are periodically
juxtaposed with two different building barriers. In general, one resonant domain in the former splits into two resonant subdomains
in the latter, and splitting occurs each time when two new barriers are added. The results indicate that the resonance splitting
is determined not only by the structure but also by the parameters of building blocks.
Received: 12 October 1997/ Revised and Accepted: 5 January 1998 相似文献
15.
M. Capone M. Grilli W. Stephan 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(4):551-557
We investigate polaron formation in a many-electron system in the presence of a local repulsion sufficiently strong to prevent
local-bipolaron formation. Specifically, we consider a Hubbard-Holstein model of interacting electrons coupled to dispersionless
phonons of frequency . Numerically solving the model in a small one-dimensional cluster, we find that in the nearly adiabatic case , the necessary and sufficient condition for the polaronic regime to occur is that the energy gain in the atomic (i.e., extremely localized) regime overcomes the energy of the purely electronic system . In the antiadiabatic case, , polaron formation is instead driven by the condition of a large ionic displacement (g being the electron-phonon coupling). Dynamical properties of the model in the weak and moderately strong coupling regimes
are also analyzed.
Received 15 February 1999 相似文献
16.
17.
Li Zhang Hong-Jing Xie Chuan-Yu Chen 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(4):577-582
Within the framework of the dielectric continuum model, interface optical(IO) and surface optical(SO) phonon modes and the
Fr?hlich electron-IO (SO) phonon interaction Hamiltonian in a multi-shell spherical system were derived and studied. Numerical
calculation on CdS/HgS/H2O and CdS/HgS/CdS/H2O spherical systems have been performed. Results reveal that there are two IO modes and one SO mode for the CdS/HgS/H2O system, one SO mode and four IO modes whose frequencies approach the IO phonon frequencies of the single CdS/HgS heterostructure
with the increasing of the quantum number l for CdS/HgS/CdS/H2O. It also showed that smaller l and SO phonon compared with IO phonon, have more significant contribution to the electron-IO (SO) phonon interaction.
Received 16 October 2001 and Received in final form 23 January 2002 Published online 25 June 2002 相似文献
18.
Y. Caglar S. Ilican M. Caglar 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(3):251-256
It has recently been shown that growth of a multilayer
structure with one or more delta-layers at high temperature leads to
spreading and asymmetrization of the dopant distribution [see, for
example, E.F.J. Schubert, Vac. Sci. Technol. A. 8, 2980 (1990), A.M. Nazmul, S. Sugahara, M. Tanaka, J. Crystal Growth 251, 303 (2003); R.C. Newman, M.J. Ashwin, M.R. Fahy, L. Hart, S.N. Holmes, C. Roberts, X. Zhang, Phys. Rev. B 54, 8769 (1996); E.F. Schubert, J.M. Kuo, R.F. Kopf, H.S. Luftman, L.C. Hopkins, N.J. Sauer, J. Appl. Phys. 67, 1969 (1990); P.M. Zagwijn, J.F. van der Veen, E. Vlieg, A.H. Reader, D.J. Gravesteijn, J. Appl. Phys. 78, 4933 (1995); W.S. Hobson, S.J. Pearton, E.F. Schubert, G. Cabaniss, Appl. Phys. Lett. 55, 1546 (1989); Delta Doping of Semiconductors, edited by E.F. Schubert (Cambridge University Press, Cambridge, 1996); Yu.N. Drozdov, N.B. Baidus', B.N. Zvonkov, M.N. Drozdov,
O.I. Khrykin, V.I. Shashkin, Semiconductors 37, 194 (2003); E. Skuras, A.R. Long, B. Vogele, M.C. Holland, C.R. Stanley, E.A. Johnson, M. van der Burgt, H. Yaguchi, J.
Singleton, Phys. Rev. B 59, 10712 (1999); G. Li, C. Jagadish, Solid-State Electronics 41, 1207 (1997)]. In this
work analytical and numerical analysis of dopant dynamics in a
delta-doped area of a multilayer structure has been accomplished
using Fick's second law. Some reasons for asymmetrization of a
delta-dopant distribution are illustrated. The spreading of a
delta-layer has been estimated using example materials of a
multilayer structure, a delta-layer and an overlayer. 相似文献
19.
Phonon conductivity in intermediately doped n-type silicon still remains unexplained. In this paper we have calculated the
phonon conductivity in Li-doped silicon for Nex < Nc using Mikoshiba's inhomogeneity model. We have introduced spherical polar coordinates for the phonon polarization vectors
in Sota and Suzuki's theory in order to take into account the realistic picture of the scattered phonons. Deformation potential
for different polarizations λ has been evaluated for the metallic region. Present calculations show that Mikoshiba's inhomogeneity
model is able to explain the phonon conductivity of Li-doped silicon having intermediate donor concentration very well.
Received 18 May 2001 / Received in final form 4 July 2002 Published online 19 December 2002
RID="a"
ID="a"e-mail: mkroy@ctgu.edu 相似文献
20.
A. Tsukernik D. Cheskis O. Potashnik A. Palevski S. Bar-Ad S. Luryi A. Cho 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(3):341-344
We have measured the dependence of the Fermi energy on carrier concentration in Sn doped InGaAs at 4.2 K and 300 K. At 4.2
K the Fermi energy was measured by photoluminescence spectroscopy, and at 300 K it was deduced from transport measurements
of thermionic emission. In both cases the dependence of the Fermi energy on the mobile electron concentration, measured by
Hall effect, strongly deviates from standard theoretical predictions, and the deviation increases with concentration. The
most striking observed anomaly is the near saturation of the Fermi level when the Hall concentration exceeds 1019 cm-3.
Received 19 April 2001 and Received in final form 22 July 2001 相似文献