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1.
J.-J. Shi B.C. Sanders S.-H. Pan 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(1):113-119
We calculate the electron-phonon scattering rate for an asymmetric double barrier resonant tunneling structure based on dielectric
continuum theory, including all phonon modes, and show that interface phonons contribute much more to the scattering rate
than do bulk-like LO phonons for incident energies which are approximately within an order of magnitude of the Fermi energy.
The maximum scattering rate occurs for incident electron energies near the quantum well resonance. Subband nonparabolicity
has a significant influence on electron-phonon scattering in these structures. We show that the relaxation time is comparable
to the dwell time of electrons in the quantum well for a typical resonant tunneling structure.
Received: 23 December 1997 / Revised: 24 March 1998 / Accepted: 9 March 1998 相似文献
2.
A. Milekhin T. Werninghaus D.R.T. Zahn Y. Yanovskii V. Preobrazhenskii B. Semyagin A. Gutakovskii 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(3):295-299
The vibrational spectrum of ultra-thin layer GaSb/AlSb superlattices was investigated in detail by infrared (IR) and Raman
spectroscopies. The effect of confinement of the transverse and longitudinal optical phonons in both types of the layers was
studied. The dispersions of optical phonons of the GaSb and the AlSb obtained from the analysis of the Raman and IR spectra
are in a good accordance with the theoretical data and results of neutron scattering experiments. First- and second-order
Raman spectroscopy indicates the presence of intermixture of atoms at the interfaces in the GaSb/AlSb superlattices.
Received: 11 May 1998 / Accepted: 21 July 1998 相似文献
3.
4.
F. Dugain M. de Boissieu K. Shibata R. Currat T.J. Sato A.R. Kortan J.-B. Suck K. Hradil F. Frey A.P. Tsai 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(4):513-516
The dynamics of the decagonal AlNiCo phase has been investigated on a single-grain quasicrystalline sample using inelastic
neutron scattering. The decagonal structure can be viewed as a periodic stacking of quasiperiodic planes. The anisotropy between
the modes propagating in the periodic and quasiperiodic directions is found to be much weaker than theoretically predicted.
A strong resonance splitting is observed at an energy transfer of 15 meV for transverse modes polarized in the quasiperiodic
plane.
Received: 18 November 1998 / Accepted: 27 November 1998 相似文献
5.
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
6.
J. Kästner W. Petry S.M. Shapiro A. Zheludev J. Neuhaus Th. Roessel E.F. Wassermann H. Bach 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(4):641-648
The acoustic phonon dispersions of two Invar crystals , one ordered with the () structure, the other disordered fcc, have been investigated between 3.4 K and 470 K by inelastic and elastic neutron scattering.
For the ordered crystal, pronounced softening of the whole
phonon branch is observed on cooling below the Curie temperature. Particularly strong phonon softening at the M-point zone
boundary of the structure leads to a displacive, antiferrodistortive phase transition at low temperatures. For the disordered crystal, much
weaker softening of the
phonons is observed and restricted to the region near the Brillouin zone center, where increasing elastic scattering with
decreasing temperature indicates the growth of local tetragonal strain. This strain is considered as a typical precursor of
the transformation to bct martensite. Specific heat measurements, performed at low temperatures on both crystals confirm the
neutron scattering results and reveal considerable enhancement of the low energy phonon density of states in the ordered crystal.
Received 18 January 1999 相似文献
7.
I. Bongrand É. Picholle C. Montes 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(1):121-127
Due to their finite numerical aperture, both longitudinal and transverse stimulated Brillouin scattering can occur in single-mode
fibers. We discuss the role of the fiber structure and propose a coherent model accounting for both effects. We show experimentally
and numerically that, in some cases, the perturbative cladding Brillouin scattering (CBS) can severely affect the dynamics
of SBS Brillouin fiber lasers. New dynamical regimes of long-fiber Brillouin ring lasers are presented, including stable trains
of modulated pulses.
Received 17 September 2001 / Received in final form 5 March 2002 Published online 28 June 2002 相似文献
8.
C. Grimaldi L. Pietronero M. Scattoni 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(2):247-255
In the theory of nonadiabatic superconductivity several features are governed by the electron-phonon vertex correction which
has a complex structure both in momentum and frequency. We derive a physical interpretation of such nonadiabatic effects that
permits to link them to specific material properties. We show how the nonadiabatic vertex correction can be decomposed into
two terms with different physical origins. In particular, the first term describes the lattice polarization induced by the
electrons and it is essentially a single-electron process whereas the second term is governed by the particle-hole excitations
due to the exchange part of the phonon-mediated electron-electron interaction. We show that by weakening the influence of
the exchange interaction the vertex takes mostly positive values giving rise to an enhanced effective coupling in the scattering
with phonons. This weakening of the exchange interaction can be obtained by lowering the density of the electrons, or by considering
only long-ranged (small q) electron-phonon couplings.
Received 23 November 1998 and Received in final form 22 January 1999 相似文献
9.
S.W.H. Eijt R. Currat J.E. Lorenzo P. Saint-Grégoire B. Hennion Y.M. Vysochanskii 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(2):169-178
The low frequency lattice dynamics and its relationship to the second order paraelectric-to-ferroelectric transition in Sn2P2S6 is studied. The dispersion branches of the acoustic and lowest lying optical phonons in the a*-c* plane have been obtained in the ferroelectric phase, for x-polarized phonons. Close to the phase transition a considerable softening is found for the lowest optical mode (Px), comparable to the behaviour observed in previous Raman investigations. As found previously in Sn2P2Se6, a strong coupling between the TO(Px) and TA(uxz) phonons is observed, although, apparently, not strong enough to lead to an incommensurate phase. The soft TO(Px) mode at the zone center is observed. The temperature dependence of its frequency and damping shows that the transition is
not entirely displacive. At low temperatures an unusual apparent negative LO-TO splitting is observed which is shown to arise
from the coupling of the x-polarized soft mode to the nearby z-polarized optical phonon. For comparison, the soft TO(Px) dispersion in the a*-b* plane is measured in both the paraelectric and ferroelectric phases. Consistent frequency changes and LO-TO splitting are
observed, revealing a significant interaction between the TA(uyx) and LA(uxx) acoustics branches and the TO and LO soft optic branches, respectively. In contrast, the nearby y-polarized optic branch shows almost no temperature dependence. Finally, the influence of piezoelectric effects on the limiting
acoustic slopes in the ferroelectric phase is discussed.
Received: 11 May 1998 / Revised and Accepted: 15 June 1998 相似文献
10.
S. Ban X.X. Liang 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(1):153-158
The interface polaron states in a heterojunction are discussed by considering an energy-band bending near the interface and
the influence of an image potential. The ground state energy and the effective mass of a polaron are variationally calculated.
The numerical results for the GaAs/
heterojunction are given. It is shown that even though the influences from bulk longitudinal optical (LO) phonons are more
important for the heterojunctions with lower Al composition, the contributions from two branches of interface optical (IO)
phonons are not negligible. For the heterojunctions with higher Al composition, both the influences from LO phonons and two
branches of IO phonons are important. The band-bending plays an important role for the interface localization of polarons,
but the influence of the image potential is not essential.
Received: 4 November 1997 / Revised and Accepted: 9 March 1998 相似文献
11.
T. Ruf 《Applied Physics A: Materials Science & Processing》2003,76(1):21-26
Inelastic X-ray scattering with meV resolution has recently become available for studies of dynamical properties and elementary
excitations in solids. Contrary to Raman spectroscopy at visible wavelengths, which in first order is limited to the Brillouin-zone
center, the wave vectors in hard X-ray Raman scattering are very large, and the crystal-momentum transfer to elementary excitations,
whose energies may range from a few meV up to several eV, can be tuned continuously across the whole Brillouin zone. This
paper reviews new and unique possibilities offered by X-ray Raman spectroscopy for crystalline solids, such as phonon-dispersion
measurements (GaN), the determination of phonon self-energies (isotopically mixed diamond), and resonance effects and studies
of electronic excitations (copper oxides).
Received: 19 October 2001 / Accepted: 12 December 2001 / Published online: 27 March 2002 / Published online: 27 March 2002
RID="*"
ID="*"Present address: Agilent Technologies Deutschland GmbH, Herrenberger Str. 130, 71034 B?blingen, Germany 相似文献
12.
A. Benyoussef D. Dohmi A. El Kenz L. Peliti 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(4):503-510
Using a replica formalism, a generalization of a recent mean field model corresponding to the observed wrinkling transition
in randomly polymerized membranes is presented. In this model we study the effects of global fluctuations of the surface normals
to the flat membrane, which can be introduced by a random local field. In absence of these global fluctuations, we show that,
the model exhibits both continuous and discontinuous transitions between flat and wrinkled phases, contrary to what has been
predicted by Bensimon et al. and Attal et al. Phase diagrams both in replica symmetry and in breaking of replica symmetry in sense of Almeida and Thouless are given. We
have also investigated the effects of global fluctuations on the replica symmetry phase diagram. We show that, the wrinkled
phase is favored and the flat phase is unstable. For large global fluctuations, the transition between wrinkled and flat phases
becomes first order.
Received: 3 December 1997 / Revised: 31 March 1998 / Accepted: 3 August 1998 相似文献
13.
14.
I. Savatinova I. Savova C.C. Ziling V. Atuchin 《Applied Physics A: Materials Science & Processing》2000,70(5):555-559
Refractive index change and Raman scattering of Z-cut proton-exchanged LiTaO3 optical waveguides with different composition have been studied. Probing of the waveguide depth was carried out by using
micro-Raman spectroscopy in order to distinguish layers with different phase states. Varying the proton-exchange and post-exchange
annealing regimes, two phases –α and β– in addition to the pure LiTaO3, were clearly observed. The behaviour of the A
1 vibrations of the TaO6 groups was found to be very sensitive to the phase changes. Using data from waveguide Raman spectra, normal and oblique E(TO,
LO) phonons were sorted and their properties were followed in the α and β phases. The OH-stretchings are considered to correspond
to dipoles turned out of the oxygen planes.
Received: 9 July 1999 / Accepted: 11 October 1999 / Published online: 24 March 2000 相似文献
15.
J. Szeftel G. Huang 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):329-334
The properties of vibrational localized (breathers) and traveling (anharmonic phonons) waves are discussed in an infinite,
one-dimensional, monoatomic crystal for the Fermi-Pasta-Ulam and Frenkel-Kontorova models. The shooting and finite difference
schemes have been implemented to reckon the displacement fields of breathers and anharmonic phonons, respectively. These tools
provide localized and traveling waves proving to be indefinitely stable in simulations carried out by solving the equations
of motion. The emphasis is laid on the role of the cubic and quartic terms of the anharmonic potential which turn out to oppose
and to shore up the restoring force, respectively. The case of vibrational modes arising in an anharmonic crystal subject
to a soft phonon induced instability is also addressed.
Received 7 November 2001 and Received in final form 5 February 2002 Published online 6 June 2002 相似文献
16.
K. Parlinski Y. Kawazoe 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(1):49-58
Using the local-density approximation, calculating the Hellmann-Feynman forces, applying the direct method and deriving the
phonon dispersion relations, the stability of the perovskite-like structures of MgSiO3 at T
=0 have been studied. The cubic Pmm phase shows a dispersion-less soft phonon branch spreading from the R to M points of the cubic Brillouin zone. This soft
branch persists up to high pressures of 150 GPa. The low-symmetry phases I4/mcm and Imma, P4/mbm can be considered as a result
of the soft mode condensation at the M and R points, respectively. These phases prove to be unstable at T
=0. The experimentally observed Pmnb phase is a consequence of the intersection of Imma and P4/mbm space groups. Thus, it can
be regarded as a simultaneous condensation of two soft modes: one at the M and a second at the R high-symmetry points of the
cubic Brillouin zone. The phonon dispersion relations of Pmnb show that this phase is stable and its optical phonons appear
above 4.0 THz only.
Received 15 October 1999 and Received in final form 14 January 2000 相似文献
17.
N. Esser 《Applied Physics A: Materials Science & Processing》1999,69(5):507-518
Only recently Raman spectroscopy (RS) has advanced into the study of surface phonons from clean and adsorbate-covered semiconductor
surfaces. RS allows the determination of eigenfrequencies as well as symmetry selection rules of surface phonons, by k-conservation limited to the Brillouin zone-center, and offers a significantly higher spectral resolution than standard surface
science techniques such as high-resolution electron energy loss spectroscopy. Moreover, surface electronic states become accessible
via electron–phonon coupling. In this article the fundamentals of Raman scattering from surface phonons are discussed and
its potential illustrated by considering two examples, namely Sb-monolayer-terminated and clean InP(110) surfaces. Both are
very well understood with respect to their atomic and electronic structure and thus may be regarded as model systems for heteroterminated
and clean semiconductor surfaces. In both cases, localized surface phonons as well as surface resonances are detected by Raman
spectroscopy. The experimental results are compared with surface modes predicted by theoretical calculations. On InP(110),
due to the high spectral resolution of Raman spectroscopy, several surface modes predicted by theory can be experimentally
verified. Surface electronic transitions are detected by changing the energy of the exciting laser light indicating resonances
in the RS cross section.
Received: 7 April 1999 / Accepted: 25 June 1999 / Published online: 16 September 1999 相似文献
18.
L. Martín-Carrón A. de Andrés 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(1):11-16
We have studied the behavior of the Raman phonons of a stoichiometric LaMnO3 single crystal as a function of temperature in the range between 77 K and 900 K. We focus on the three main phonon peaks
of the Pbnm structure, related to the tilt, antisymmetric stretching (Jahn-Teller mode) and stretching modes of Mn-O octahedra.
The phonon frequencies show a strong softening that can be fit taking into account their renormalization because of three
phonon anharmonic effects in the pseudoharmonic approximation. Thermal expansion effects, in particular the variation of Mn-O
bond lengths with temperature, are not relevant above 300 K. On the contrary, phonon width behavior deviates from the three
phonon scattering processes well bellow T
c
. The correlation between the magnitude of the cooperative Jahn-Teller distortion, that disappears at 800 K, and the amplitude
of the Raman phonons in the orthorhombic phase is shown. Nevertheless, Pbnm phonons are still observable above this temperature.
Phonon width and intensity behavior around T
c
can be explained by local melting of the orbital order that begins quite below T
c
and by fluctuations of the regular Mn-O octahedra that correspond to dynamic Jahn-Teller distortions.
Received 25 January 2001 and Received in final form 14 March 2001 相似文献
19.
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
20.
S. Fujimoto N. Kawakami 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):389-393
The effects of Umklapp scattering on the zero-temperature conductance in one-dimensional quantum wires are reexamined by taking
into account both the screening of external potential and the non-uniform chemical potential shift due to electron-electron
interaction. It is shown that in the case away from half-filling the conductance is given by the universal value, 2e
2
/h, even in the presence of Umklapp scattering, owing to these renormalization effects of external potential. The conclusion
is in accordance with the recent claim obtained for the system with non-interacting leads being attached to a quantum wire.
Received: 5 February 1998 / Received in final form: 16 March 1998 / Accepted: 17 April 1998 相似文献