共查询到20条相似文献,搜索用时 15 毫秒
1.
K. Chah M.D. Fontana M. Aillerie P. Bourson G. Malovichko 《Applied physics. B, Lasers and optics》1998,67(1):65-71
3 along the ferroelectric c axis in pure and chromium-doped crystals. We have studied four series of samples with various crystal
compositions and doping concentrations to separate the influence of the intrinsic defects related to the non-stoichiometry
and the effect of the introduction of chromium. In pure and slightly doped crystals, the electro-optic coefficient rc shows a non-monotonous dependence on the controlled crystal composition, which reflects a similar behaviour of the corresponding
dielectric permittivity. In the highly Cr-doped crystals rc displays a large decrease with increasing Cr concentration whatever the crystal composition. The results have been discussed
by means of the LiNbO3 structure and the substitution site dynamics.
Received: 14 November 1997/Accepted: 2 January 1998 相似文献
2.
A.V. Hamza M.W. Newman P.A. Thielen H.W.H. Lee T. Schenkel J.W. McDonald D.H. Schneider 《Applied Physics A: Materials Science & Processing》2003,76(3):313-317
The intense, ultra-fast electronic excitation of clean silicon (100)–(2×1) surfaces leads to the formation of silicon nanostructures
embedded in silicon, which photoluminesce in the yellow-green (∼2-eV band gap). The silicon surfaces were irradiated with
slow, highly charged ions (e.g. Xe44+ and Au53+) to produce the ultra-fast electronic excitation. The observation of excitonic features in the luminescence from these nanostructures
has recently been reported. In this paper we report the dispersion of the excitonic features with laser excitation energy.
A phonon-scattering process is proposed to explain the observed dispersion.
Received: 2 October 2001 / Accepted: 18 July 2002 / Published online: 25 October 2002
RID="*"
ID="*"Corresponding author. Fax: +1-925/423-7040, E-mail: Hamza1@llnl.gov
RID="**"
ID="**"Present address: University of California, Lawrence Berkeley National Laboratory, Berkeley, CA 94 720, USA 相似文献
3.
Z.G. Koinov 《Physics letters. A》2007,371(4):322-326
By solving the BCS and Bethe-Salpeter equations, we confirm the result by Chu and Chang that a secondary peak appears in the optical absorption spectrum immediately after the 1S-exciton peak in the presence of a condensed phase. The observation of the secondary peak indicates the presence of exciton condensate. 相似文献
4.
We reconsider the semiconductor trions from scratch. We first determine the very many “reasonable” ways to write the trions
in first quantization. We then select the forms which are easy to relate to physical pictures. In a second part, we derive
the corresponding creation operators in second quantization. We pay particular attention to the expression of the X- trion in terms of exciton and free-electron, as it is the one adapted to future works on many-body effects with trions.
Received 27 May 2002 / Received in final form 18 December 2002 Published online 20 June 2003
RID="a"
ID="a"e-mail: combescot@gps.jussieu.fr 相似文献
5.
O. Betbeder-Matibet M. Combescot 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(4):517-523
Pauli exclusion between the carriers of N excitons induces novel many-body effects, quite different from the ones generated by Coulomb interaction. Using our commutation
technique for interacting close-to-boson particles, we here calculate the Hamiltonian expectation value in the N-ground-state-exciton state. Coulomb interaction enters this quantity at first order only by construction; nevertheless, due
to Pauli exclusion, subtle many-body effects take place, which give rise to terms in (Na
x
3/)n with n ≥ 2. An exact procedure to get these density dependent terms is given.
Received 11 February 2002 / Received in final form 30 May 2002 Published online 6 March 2003
RID="a"
ID="a"e-mail: combescot@gps.jussieu.fr 相似文献
6.
O. Betbeder-Matibet M. Combescot 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(4):505-516
The correct treatment of the close-to-boson character of excitons is known to be a major problem. In a previous work, we have
proposed a “commutation technique” to include this close-to-boson character in their interactions. We here extend this technique
to excitons with spin degrees of freedom as they are of crucial importance for many physical effects. Although the exciton
total angular momentum may appear rather appealing at first, we show that the electron and hole angular momenta are much more
appropriate when dealing with scattering processes. As an application of this commutation technique to a specific problem,
we reconsider a previous calculation of the exciton-exciton scattering rate and show that the proposed quantity is intrinsically
incorrect for fundamental reasons linked to the fermionic nature of the excitons.
Received 25 October 2001 Published online 25 June 2002 相似文献
7.
O. Betbeder-Matibet M. Combescot 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(1):17-29
We study the interaction of an exciton with a distant metal, which is the simplest problem on interacting excitons: The semiconductor
and metal electrons being “different” species, we do not have to worry about the tricky consequences of Pauli exclusion between
identical carriers, which appear in any other problem on interacting excitons. We show how the exciton absorption, in the
presence of semiconductor-metal interaction, can be derived in a very simple and transparent way from an exciton diagram procedure,
provided that we use the appropriate exciton-metal interaction vertex, which contains the scattering from an exciton state
to another exciton state under a Coulomb excitation. We also show that the resolution of this problem using standard electron-hole
diagrams is dreadfully complicated at the lowest order in the semiconductor-metal interaction already, preventing a full calculation
of the exciton-metal coupling from this usual technique.
Received 26 February 2001 相似文献
8.
Resonant optical excitation of a direct bandgap semiconductor below the band edge induces excitonic coherences. Experiments
based on transient four-wave mixing or cw spectral-hole burning provide an excellent approach to eliminate inhomogeneous broadening
and enable determination of the time scale and origin of the decay of the optically induced quantum coherence. Such measurements
are of interest in basic physics since they reflect fundamental interactions between the exciton and the surrounding environment
including, for example, lattice vibrations and interface fluctuations. They also relate to potential applications of these
excitations such as in coherent control or quantum information processing.
Received: 30 March 2000 / Accepted: 2 September 2000 / Published online: 12 October 2000 相似文献
9.
Nonlinear absorption properties of Co2+:MgAl2O4 crystal 总被引:2,自引:0,他引:2
K.V. Yumashev I.A. Denisov N.N. Posnov P.V. Prokoshin V.P. Mikhailov 《Applied physics. B, Lasers and optics》2000,70(2):179-184
The differential absorption spectra of Co2+: MgAl2O4 (MALO) crystal were studied with a picosecond pump-probe technique under excitation of the 4A2→4T1(4P) and 4A2→4T1(4F) transitions of the tetrahedral Co2+ ion. The difference spectra of stimulated emission (SE) and excited state absorption (ESA) were derived from the measured
differential absorption spectra. The 4T1(4P)→4A2 SE band around 660 nm was observed. The ESA bands were assigned to the 4T2→4T1(4P) transition and to transitions from the thermally populated 2E(2G) excited state to doublet levels arising from the 2F free-ion level of the tetrahedrally coordinated Co2+ ion. Absorption saturation measurements were performed at 1.34 μm and 1.54 μm. Passive Q-switching of 1.34-μm Nd3+:YAlO3 and 1.54-μm Er3+:glass lasers was realized using the Co2+:MALO crystal as saturable absorber. The Q-switched laser pulses of 38 ns (110 ns) in duration and up to 2.7 mJ (10 mJ) in
energy at 1.54 μm (1.34 μm) were obtained.
Received: 3 March 1999 / Revised version: 30 June 1999 / Published online: 30 November 1999 相似文献
10.
Takeshi Yasuda Masatoshi Saito Hiroaki Nakamura Tetsuo Tsutsui 《Applied Physics A: Materials Science & Processing》2009,95(1):179-183
We have studied the electronic excitations of fluorinated copper phthalocyanine, CuPcF16, thin films using electron energy-loss spectroscopy in transmission. This allowed for the derivation of the dielectric function
in a wide energy range. Furthermore, we have analyzed the lowest excitation feature using a Lorentz model, which enabled the
determination of the dielectric background in the energy range of the gap excitation, and an analysis of the momentum dependence
of the spectral intensities at low energies. 相似文献
11.
Size dependence of non-linear optical properties of SiO2 thin films containing InP nanocrystals 总被引:1,自引:0,他引:1
M.J. Zheng L.D. Zhang J.G. Zhang 《Applied Physics A: Materials Science & Processing》2001,73(2):183-187
SiO2 composite thin films containing InP nanocrystals were fabricated by radio-frequency magnetron co-sputtering technique. The
microstructure of the composite thin films was characterized by X-ray diffraction and Raman spectrum. The optical absorption
band edges exhibit marked blueshift with respect to bulk InP due to strong quantum confinement effect. Non-linear optical
absorption and non-linear optical refraction were studied by a Z-scan technique using a single Gaussian beam of a He-Ne laser
(632.8 nm). We observed the saturation absorption and two-photon absorption in the composite films. An enhanced third-order
non-linear optical absorption coefficient and non-linear optical refractive index were achieved in the composite films. The
nonlinear optical properties of the films display the dependence on InP nanocrystals size.
Received: 27 June 2000 / Accepted: 27 June 2000 / Published online: 13 September 2000 相似文献
12.
In this work, an analytical expression for the complex dielectric function is proposed, which includes both discrete and continuum
exciton effects. We have introduced Lorentzian broadening in Elliott’s formula and compare our model to other models based
on Elliott’s formula. The results show that our model is superior to other models for the dielectric function of ZnO in the
literature. Excellent agreement with experimental data for the dielectric function of ZnO for both perpendicular and parallel
polarizations has been obtained using our model.
Received: 18 April 2001 / Accepted: 19 December 2001 / Published online: 20 March 2002 / Published online: 20 March 2002
RID="*"
ID="*"Corresponding author. (Fax: +852-2559-8738, E-mail: dalek@eee.hku.hk) 相似文献
13.
O.M. Schmitt D.B. Tran Thoai P. Gartner H. Haug 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(2):217-222
The dephasing and relaxation kinetics of bosonic excitons interacting with a thermal bath of acoustic phonons is studied after
coherent pulse excitation. The kinetics of the induced excitonic polarization is calculated within Markovian equations both
for subcritical and supercritical excitation with respect to a Bose-Einstein condensation (BEC). For excited densities n below the critical density , an exponential polarization decay is obtained, which is characterized by a dephasing rate . This dephasing rate due to phonon scattering shows a pronounced exciton-density dependence in the vicinity of the phase
transition. It is well described by the power law that can be understood by linearization of the equations around the equilibrium solution. Above the critical density we get
a non-exponential relaxation to the final condensate value p0 with that holds for all densities. Furthermore we include the full self-consistent Hartree-Fock-Bogoliubov (HFB) terms due to
the exciton-exciton interaction and the kinetics of the anomalous functions . The collision terms are analyzed and an approximation is used which is consistent with the existence of BEC. The inclusion
of the coherent exciton-exciton interaction does not change the dephasing laws. The anomalous function Fk exhibits a clear threshold behaviour at the critical density.
Received 13 December 1999 相似文献
14.
In this work we propose an analytical expression for the complex dielectric function which includes both discrete and continuum
exciton effects. We have introduced Lorentzian broadening into Elliott’s formula. The introduction of broadening leads to
equations for the dielectric function containing only elementary functions. We have applied the proposed model to the dielectric
function of wurtzite GaN in the spectral region 1–10 eV. Excellent agreement with the experimental data has been obtained.
We show that the Lorentzian-broadened dielectric function decays more slowly than the experimental data for hexagonal GaN
at the low-energy side. This indicates that the broadening of the absorption edge in GaN is not purely Lorentzian. The agreement
with the experimental data can be improved using adjustable broadening modification.
Received: 29 January 2001 / Accepted: 30 May 2001 / Published online: 25 July 2001 相似文献
15.
We propose the Bose-Einstein condensation and superfluidity of quasi-two-dimensional spatially indirect magnetobiexcitons in a slab of superlattice with alternating electron and hole layers consisting from the semiconducting quantum wells (QWs) and graphene superlattice in high magnetic field. For this system the instability of the ground state of interacting two-dimensional indirect magnetoexcitons in a slab of superlattice with alternating electron and hole layers in high magnetic field is found. The density of superfluid component ns(T) and the temperature of the Kosterlitz-Thouless phase transition to the superfluid state in the system of two-dimensional indirect magnetobiexcitons, interacting as electrical quadrupoles, are obtained for both QW and graphene realizations. 相似文献
16.
H.M. Wong Jian-Bai Xia K.W. Cheah 《Applied Physics A: Materials Science & Processing》1997,64(5):507-509
Received: 10 June 1996/Accepted: 20 October 1996 相似文献
17.
L. Samson I. Ippolito G.G. Batrouni J. Lemaitre 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(3):377-385
We report on experiments studying the statistical properties of the motion of balls on a bumpy surface. This motion is found
to be diffusive. In the direction of the mean flow, the coefficient of diffusion is found to attain a constant value, independent
of the size of the ball and the inclination angle. The diffusion transverse to the mean flow is characterized by a coefficient
which decreases with the inclination of the plane, and scales with the size of moving ball.
Received: 13 March 1997 / Revised: 10 December 1997 / Accepted: 17 February 1998 相似文献
18.
The applied Boltzmann relaxation kinetics for stationary and ps-pulsed nonresonant pumping takes the polariton-acoustic phonon and the polariton-polariton scattering into account. For cavities with a vacuum Rabi splitting around , we find for ps-pulse excitation a transient bosonic condensation in the ground state. For microcavities with a large vacuum Rabi splitting of we find for zero detuning, due to the steep increase of radiative losses, a condensation with a macroscopically occupied state in the wavenumber region at which the Bragg mirrors become transparent. With positive detunings which increase the scattering rates, the finite-size Bose-Einstein condensation in the ground state is restored. 相似文献
19.
G.P. Malik Raman K. Jha V.S. Varma 《The European Physical Journal A - Hadrons and Nuclei》1998,3(4):373-375
The study of meson formation in quark-gluon plasma using a temperature-dependent Bethe-Salpeter formalism presented earlier,
is now extended to a logarithmic and a combination of a Coulomb plus a square-root kernel. We are able to get good fits to
the meson masses with both kinds of kernels and our present results are qualitatively similar to those obtained for the Coulomb
plus a linear kernel.
Received: 9 February 1998 / Revised version: 27 April 1998 相似文献
20.
Thomas G. Pedersen 《Solid State Communications》2007,141(10):569-572
Wannier excitons polarized by a static electric field and confined to low-dimensional structures are studied. Effective non-integer dimensions are included by considering hydrogenic states in α-dimensional space, with α as a parameter. Exact expressions for lowest order energy and wave function corrections are obtained as a function of α. For the 1s state, we demonstrate that the exciton polarizability decreases with reduced dimensionality and eventually vanishes as (α−1)4 as the 1D limit is approached. The low-dimensional 2s and 2p polarizabilities are also decreased but remain finite in the 1D limit. 相似文献