共查询到20条相似文献,搜索用时 15 毫秒
1.
C. Voisin D. Christofilos N. Del Fatti F. Vallée 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):139-144
Femtosecond excitation and relaxation of nonequilibrium electrons are investigated in silver clusters using a two color pump-probe
technique with resonant excitation of the surface plasmon resonance and off resonant probing. The excitation process is shown
to be identical to that in metal films, and permits creation of a strongly athermal single electron excitation in a time scale
shorter than the duration of the pulses (25-30 fs), in agreement with the free-electron absorption model. Following the time
evolution of the nonequilibrium distribution yields information on the internal energy redistribution dynamics of the conduction
electrons and of its modification by confinement in metal clusters.
Received 1st December 2000 相似文献
2.
Yu-Lin Gao Yi-Jun Lu Jian-Sheng Zheng Zhi-Gang Cai Hai-Yu Sang Xue-Ran Zeng 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(2):145-148
The time-resolved photoluminescence spectra of ordered and disordered Ga0.52In0.48P alloys were studied at room temperature and at 77 K liquid nitrogen, respectively. The ordered samples have well fitted
two exponential processes decay curves and the time constants are sample dependent and have little relationship with the ordering
degree. The decay curve of disordered sample shows that it has single exponential process and its lifetime has a tendency
of reduction with the decrease of excitation intensity. The photoluminescence spectra with different delay time at 77 K show
that the ordered samples exhibit about 6 ∼ 10 meV blue-shift of PL peak energy with the delay time.
Received 13 December 2001 Published online 19 July 2002 相似文献
3.
J. Bellessa V. Voliotis T. Guillet D. Roditchev R. Grousson X.L. Wang M. Ogura 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(4):499-505
We report on time-resolved microphotoluminescence experiments in a single GaAs/GaAlAs V-shaped quantum wire as a function
of optical excitation intensity. At low pump power we observe that excitons are localized in quantum boxes formed by the local
potential minima existing along the wire axis. As the pump power is increased, state filling of the lowest lying levels of
the boxes appears. When two carriers occupy the first excited level of the box, a very efficient Auger scattering occurs,
leading to a transfer of carriers from one box to another neighbouring one. The intradot Auger scattering time has been measured
and is of the same order of magnitude as the LA-phonon emission rate.
Received 5 February 2001 相似文献
4.
P. Foggi P. Bartolini M. Bellini M.G. Giorgini A. Morresi P. Sassi R.S. Cataliotti 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(2):143-151
The relaxation dynamics of pure acetonitrile isotopomers has been investigated in the temperature range 8 to 75 °
C. The overall response of the liquid is measured either recording directly the decay of the optical Kerr signal with heterodyne
detection (OHD-OKE) and Fourier transforming the depolarized Rayleigh scattering spectra (DRS). The OHD-OKE signals show a
decay that can be described by a bi-exponential law. At some temperatures, stressing to a maximum level the sensitivity of
the OHD-OKE experimental set-up, a damped oscillation is observed on top of the fast decay component. The two techniques provide
same results with a high level of reproducibility, as far as the slow component is concerned. This latter is described by
an exponential law with the time constants ranging in the interval 2.0 to 0.85 ps in the light and approximately in the same
interval in the deuterated molecule. The decays are, at all temperatures, well reproduced by the extended diffusion J-model. The fast component, better observed with the OHD-OKE experiments in a restricted temperature range, has time constants
ranging from 550 to 350 fs. After the subtraction of the curve due to the slower decay component, the data have also been
analyzed by Fourier transforming the fast part of the decay. The spectrum then consists of a broad (approximately 80 cm-1 wide) band centered at 50 cm-1. This band is interpreted as the manifestation of intermolecular vibrational motions.
Received 21 July 2002 Published online 1st October 2002
RID="a"
ID="a"e-mail: foggi@colonnello.lens.unifi.it 相似文献
5.
K. Vetter 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):265-269
Gamma-ray tracking in a closed array of highly segmented HPGe detectors is a new concept for the detection of γ-radiation.
Each of the interacting γ-rays is identified and separated by measuring the energies and positions of individual interactions
and by applying tracking algorithms to reconstruct the scattering sequences, even if many γ-rays hit the array at the same
time. The three-dimensional position and the energy of interactions are determined by using two-dimensionally segmented Ge
detectors along with pulse-shape analysis of the signals. Such a detector will have new and much improved capabilities compared
to current γ-ray spectrometer. One implementation of this concept, called GRETA (Gamma-Ray Energy Tracking Array), is currently
being under development at LBNL.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: kvetter@lbl.gov 相似文献
6.
Y. Pavlyukh W. Hübner 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(2):239-246
We present a method for the numerical investigation of the electron dynamics in small metallic clusters in intense laser fields.
We obtain information about collective excitations and relaxation processes in the Na
9
+
and Pt3 clusters analyzing the power spectrum of the dipole moment within a mean-field approach. The power spectrum is computed for
various laser pulse parameters as well as for the limit of an infinitely short laser pulse. Due to the basis set expansion
of the wave function our method is capable to follow the dynamics not only of the whole electron cloud, but of any particular
molecular orbital.
Received 28 March 2002 / Received in final form 31 May 2002 Published online 24 September 2002
RID="a"
ID="a"e-mail: pavlyukh@mpi-halle.de 相似文献
7.
U. Hohenester P. Kocevar N.E. Hecker R. Rodrigues-Herzog 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(1):143-152
We present a systematic study of the dependence of the energy relaxation of photo-excited minority electrons on the doping
concentration in highly p-doped GaAs. A nonmonotonic dependence is found in the region where the characteristics of the carrier-carrier interaction
changes from plasmon-mediated to quasistatically screened. Using a detailed Monte-Carlo study we are able to attribute this
observation to a general property of plasmas at high density.
Received: 1st April 1998 / Revised: 6 May 1998 /
Accepted: 18 May 1998 相似文献
8.
G. Savona D.V. Livanov A.A. Varlamov 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(4):415-420
We study the fluctuation-induced magnetotransport of a two-dimensional superconductor in the quasiballistic regime, where
ξ
GL(T) ≪ ℓ (ℓ is the electron mean free path and ξ
GL(T) is the Ginzburg-Landau coherence length). The magnetoconductivity is evaluated in the nonlocal fluctuation regime thereby
extending the existing theory valid in the local limit. We show that the Maki-Thompson (MT) and density-of-states (DOS) contributions
strongly compensate each other and their sum is negligible in comparison with the Aslamazov-Larkin (AL) term. The hierarchy
of the fluctuation contributions to the magnetoconductivity in the high-field limit is also qualitatively discussed.
Received 10 July 2002 / Received in final form 21 November 2002 Published online 7 May 2003 相似文献
9.
H.V. Klapdor-Kleingrothaus Yu.G. Zdesenko 《The European Physical Journal A - Hadrons and Nuclei》1998,3(2):107-108
We suggest here the use of ice as shielding material in the large scale GENIUS experiment for the ultimate sensitive double
beta decay and dark matter search. The idea is to pack a working volume of several tons of liquid nitrogens, which contains
the “naked” Ge detectors, inside an ice shielding. Very thin plastic foil would be used in order to prevent leakage of the
liquid nitrogen. Due to the excellent advantages of ice shielding (high purity and low cost, self-supporting ability, thermo-isolation
and optical properties, safety) this could be another possible way of realization of the GENIUS project.
Received: 30 July 1998 相似文献
10.
M. Auslender E. Kogan 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(4):525-529
We study density of states and conductivity of the doped double-exchange system, treating interaction of charge carriers both
with the localized spins and with the impurities in the coherent potential approximation. It is shown that under appropriate
conditions there is a gap between the conduction band and the impurity band in paramagnetic phase, while the density of states
is gapless in ferromagnetic phase. This can explain metal-insulator transition frequently observed in manganites and magnetic
semiconductors. Activated conductivity in the insulator phase is numerically calculated.
Received 13 June 2000 and Received in final form 5 January 2001 相似文献
11.
C. Giannetti G. Ferrini S. Pagliara G. Galimberti F. Banfi E. Pedersoli F. Parmigiani 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(1):121-125
The non-linear photoelectron spectra obtained by short
laser pulses from a Ag(100) surface show a high-energy electron
emission due to an athermal electron distribution created by the
laser pulse. By comparing the photoemission at normal and
non-normal emission geometry it is possible to evidence the
independence of the hot electron photoemission on the parallel
momentum and on different final-state configurations. A
photoemission correlation measurement evidences that
non-photoelectric effects, as tunneling or thermally assisted
photoemission, do not contribute to the electron yield. Various
theoretical models are discussed on the basis of the present
data. 相似文献
12.
P. Schwab R. Raimondi 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(4):483-495
We show that in the metallic phase of a two dimensional electron gas the spin-orbit coupling due to structure inversion asymmetry
leads to a characteristic anisotropy in the magnetoconductance. Within the assumption that the metallic phase can be described
by a Fermi liquid, we compute the conductivity in the presence of an in-plane magnetic field. Both the spin-orbit coupling
and the Zeeman coupling with the magnetic field give rise to two spin subbands, in terms of which most of the transport properties
can be discussed. The strongest conductivity anisotropy occurs for Zeeman energies of the order of the Fermi energy corresponding
to the depopulation of the upper spin subband. The energy scale associated with the spin-orbit coupling controls the strength
of the effect. More in particular, we find that the detailed behavior and the sign of the anisotropy depends on the underlying
scattering mechanism. Assuming small angle scattering to be the dominant scattering mechanism our results agree with recent
measurement on Si-MOSFET's in the vicinity of the metal-insulator transition.
Received 11 July 2001 相似文献
13.
M.W. Wu C.Z. Ning 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(3):373-376
A new spin dephasing mechanism is proposed for semiconductors with carrier momentum-dependent transition energies (inhomogeneous
broadening) between spin states. In the presence of this inhomogeneous broadening of the spin transitions, spin-conserving
(SC) scatterings lead to irreversible spin dephasing in a complete analogy to the optical dephasing of inhomogeneously broadened
optical transitions. This phenomenon is demonstrated for the case when the g-factor becomes electron-energy dependent.
Received 29 June 2000 相似文献
14.
B.S. Pavlov I.Yu. Popov S.V. Frolov 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(2):283-287
The problem of construction of quantum multiplexer is discussed. A possible construction based on resonance transport properties
of quantum waveguides coupled through small windows is considered. Small apertures play double role of “connecting channels"
and “resonant elements". Transmission coefficients for the system are determined. The workability of the device as a quantum
switch to one of three (or to two of three) channels is discussed. Control parameters for the switch are electron energy and
bias voltage.
Received 13 August 2000 and Received in final form 19 February 2001 相似文献
15.
S. Anantha Ramakrishna N. Kumar 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(4):515-519
We re-examine and correct an earlier derivation of the distribution of the Wigner phase delay time for wave reflection from
a long one-dimensional disordered conductor treated in the continuum limit. We then numerically compare the distributions
of the Wigner phase delay time and the dwell time, the latter being obtained by the use of an infinitesimal imaginary potential
as a clock, and investigate the effects of strong disorder and a periodic (discrete) lattice background. We find that the
two distributions coincide even for strong disorder, but only for energies well away from the band-edges.
Received 11 June 2001 and Received in final form 30 July 2001 相似文献
16.
F.B. Anders M. Huth 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(4):491-499
We present calculations of the electronic transport properties of heavy-fermion systems within a semi-phenomenological approach
to the dynamical mean field theory. In this approach the dynamics of the Hund's rules 4f (5f )-ionic multiplet split in a crystalline environment is taken into account. Within the scope of this calculation we use the
linear response theory to reproduce qualitative features of the temperature-dependent resistivity and hall conductivity, the
magneto-resistivity and the thermoelectric power typical for heavy-fermion systems. The model calculations are directly compared
with experimental results on CeCu
2
Si
2.
Received 30 June 2000 and Received in final form 15 December 2000 相似文献
17.
T. Franosch A. Latz R.M. Pick 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(2):229-246
The constitutive equations for the orientational dynamics of a liquid formed of linear molecules are derived microscopically.
The resulting generalised Langevin equations coincide with the phenomenological approach of Dreyfus et al. [1]. Formally exact expressions are given for the phenomenological coefficients and various constraints are shown to be consequences
of this microscopic approach.
Received 14 August 2002 Published online 4 February 2003
RID="a"
ID="a"e-mail: franosch@hmi.de 相似文献
18.
P. Schwab R. Raimondi 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(4):525-540
We derive a formula for the quantum corrections to the electrical current for a metal out of equilibrium. In the limit of
linear current-voltage characteristics our formula reproduces the well known Altshuler-Aronov correction to the conductivity
of a disordered metal. The current formula is obtained by a direct diagrammatic approach, and is shown to agree with what
is obtained within the Keldysh formulation of the non-linear sigma model. As an application we calculate the current of a
mesoscopic wire. We find a current-voltage characteristics that scales with eV/kT, and calculate the different scaling curves for a wire in the hot-electron regime and in the regime of full non-equilibrium.
Received 13 June 2001 相似文献
19.
A. Laraoui V. Halté M. Vomir J. Vénuat M. Albrecht E. Beaurepaire J.-Y. Bigot 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):251-253
We have studied the ultrafast magneto-optical response of
CoPt3 ferromagnetic nanodots with diameters ranging from 0.2 to 1 μm. Our experiments combine an accurate temporal resolution using
femtosecond laser pulses and a high spatial resolution (
300 nm)
obtained with a reflective confocal Kerr microscope. Our experimental
approach allows exploring the dynamics of the magnetization of magnetic
nanostructures over a broad temporal scale ranging from 100 fs to 1 ns. We
report the corresponding relaxation behavior of the electrons and the spins
initially excited with a large excess energy above the Fermi level. 相似文献
20.
J.C. Cao X.L. Lei 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(4):553-559
We have extended the balance equations to account for conduction-valence interband impact ionization (II) process induced
by an intense terahertz (THz) electromagnetic irradiation in semiconductors, and applied them to study the II effect on electron
transport and electron-hole pair generation-recombination rate in THz-driven InAs/AlSb heterojunctions (HJ). As many as needed
multiphoton channels are self-consistently taken into account for yielding a given accuracy. The time evolution of transport
state including THz-radiation-induced II process are monitored in details by an extensive time-dependent analysis. Two different
physical stages, the quasi-steady state and the complete steady-state, are clearly identified from the present calculations.
Intersubband electron transfer rate and net electron-hole generation rate are derived as functions of the THz radiation strength
E
ac for various radiation frequencies from f
ac = 0.42 to 6 THz at lattice temperatures T = 6 K. It's indicated that the THz radiation with a larger E
ac or a lower f
ac, has a stronger effect on electron transport and II process. Qualitative agreement is obtained between the calculated electron-hole
generation rate and the available experimental data for InAs/AlSb HJ's at T = 6 K.
Received 24 May 2002 / Received in final form 26 August 2002 Published online 31 October 2002
RID="a"
ID="a"e-mail: jccao8@hotmail.com 相似文献