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1.
Dielectric relaxation measurements of formamide (FMD)-N,N-dimethylaminoethanol (DMAE) solvent mixtures have been carried out over the entire concentration range using time domain
reflectometry technique at 25, 35 and 45°C in the frequency range of 10 MHz to 20 GHz. The mixtures exhibit a principle dispersion
of the Davidson-Cole relaxation type at microwave frequencies. Bilinear calibration method is used to obtain complex permittivity
ɛ*(ω) from complex reflection coefficient ρ*(ω) over the frequency range of 10 MHz to 10 GHz. The excess permittivity (ɛ
E), excess inverse relaxation time (1/τ)E, Kirkwood correlation factor (g
eff), activation energy and Bruggeman factor (f
B) are also calculated to study the solute-solvent interaction.
相似文献
2.
The energy spectra of traps in NaCl crystals have been studied in detail by the method of thermoluminescence. Crystals of
NaCl were undoped but treated thermally in different ways. The activation energies of traps form a single oscillator series,
E
n
=ℏω
TL
(n+1/2), ℏω
TL
=903 cm-1. Contrary to other previously studied crystals with complex lattices, the corresponding line ℏω
Ram
=ℏω
TL
was not found in Raman spectra of NaCl. It is assumed that the oscillator rule is governed by the polaron nature of traps.
The trap activation energy is determined by the vibration level from which the transition of the charge carrier to the excited
luminescence centre is made possible and depends on the distance between these centres. 相似文献
3.
A. Yu. Kudzin M. D. Volnyanskii M. P. Trubitsyn I. A. Busoul 《Physics of the Solid State》1998,40(12):1994-1997
The dielectric permittivity of Ni-doped Li2Ge7O15 crystals was studied in the vicinity of the ferroelectric phase transition. Introduction of Ni has been shown to suppress
the dielectric anomaly and to reduce substantially the transition temperature. A temperature hysteresis in ɛ (T) has been observed in nominally pure and Ni-doped Li2Ge7O15 crystals near the transition point. Measurements performed under cooling from the paraphase reveal dispersion of dielectric
permittivity at Debye relaxation frequencies of the order of 104–105 Hz at T
c
. It is proposed that the hysteresis phenomena and the low-frequency dispersion are caused by residual defects (of the type
of random local fields), which become polarized in the ferroelectric phase and become disordered above T
c
.
Fiz. Tverd. Tela (St. Petersburg) 40, 2198–2201 (December 1998) 相似文献
4.
J. K. Baria 《Czechoslovak Journal of Physics》2004,54(4):469-485
A model pseudopotential depending on an effective core radius but otherwise parameter free is used to study the interatomic
interactions, phonon dispersion curves (inq and r-space analysis), phonon density of states, mode Grüneisen parameters, dynamical elastic constants (C
11,C
12 andC
44), bulk modulus (B), shear modulus (C′), deviation from Cauchy relation (C
12–C
44), Poisson’s ratio (σ), Young’s modulus (Y), behavior of phonon frequencies in the elastic limit independent of the direction (Y
1), limiting value in the [110] direction (Y
2), degree of elastic anisotropy (A), maximum frequencyω
max, mean frequency 〈ω〉, 〈ω
2〉1/2=(〈ω〉/〈ω
−1〉)1/2, fundamental frequency 〈ω
2〉, and propagation velocities of the elastic constants in Cu, Ag, Au, Ni, Pd, and Pt. The contribution of s-like electrons
is calculated in the second-order perturbation theory for the model potential while that of d-like electrons is taken into
account by introducing repulsive short-range Born-Mayer like term. Very recently proposed screening function due to Sarkar
et al. has been used to obtain the screened form factor. The theoretical results are compared with experimental findings wherever
possible. A good agreement between theoretical investigations and experimental findings has proved the ability of our model
potential for predicting a large number of physical properties of transition metals. 相似文献
5.
Xin-Hai Liu Xue-Hua Wang Ben-Yuan Gu 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(1):37-41
The collective charge density excitations in asymmetric double-quantum-well (DQW) structures with different tunneling strengths
are systematically studied. In particular, the damping properties of the plasmon modes in various tunneling strengths are
investigated in detail. It is shown that plasmon modes in asymmetric DQW structures are quite different from those in symmetric
DQW systems. In weak tunneling regime, an intra-subband mode ω
- with an acoustic-like dispersion relation which is damped in symmetric DQW structures arises and coexists with the optical-like
mode ω
+ while the inter-subband mode ω
10 is highly damped. With the tunneling strength being increased, the ω
10 branch gradually becomes undamped and emerges out of the (1-0) single-particle continuum, whereas the ω
- branch gradually approaches the (0-0) single-particle continuum. In intermediate coupling regime, these three branches of
modes coexist undamped. In strong tunneling regime, ω
- enters the (0-0) single-particle continuum and becomes damped. Consequently, only the ω
+ and ω
10 modes exist in this regime.
Received 10 July 2001 and Received in final form 17 September 2001 相似文献
6.
L. Bartosch P. Kopietz 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):29-36
We consider the effect of Coulomb interactions on the average density of states (DOS) of disordered low-dimensional metals
for temperatures T and frequencies ω smaller than the inverse elastic life-time 1/τ. Using the fact that long-range Coulomb interactions in two dimensions (2d) generate ln2-singularities in the DOS ν(ω) but only ln-singularities in the conductivity σ(ω), we can re-sum the most singular contributions
to the average DOS via a simple gauge-transformation. If σ(ω) > 0, then a metallic Coulomb gapν(ω) ∝ |ω|/e
4 appears in the DOS at T = 0 for frequencies below a certain crossover frequency Ω
2 which depends on the value of the DC conductivity σ(0). Here, - e is the charge of the electron. Naively adopting the same procedure to calculate the DOS in quasi 1d metals, we find ν(ω) ∝ (|ω|/Ω
1)1/2exp(- Ω
1/|ω|) at T = 0, where Ω
1 is some interaction-dependent frequency scale. However, we argue that in quasi 1d the above gauge-transformation method is on less firm grounds than in 2d. We also discuss the behavior of the DOS at finite temperatures and give numerical results for the expected tunneling conductance
that can be compared with experiments.
Received 28 August 2001 / Received in final form 28 January 2002 Published online 9 July 2002 相似文献
7.
A microscopic theory of the Efetov supermatrix sigma-model type is constructed for the low-lying electron states in a mixed
superconductive-normal system with disorder. This technique is used for the study of the localized states in the core of a
vortex in a moderately clean superconductor with τ
−1≫ω
0∼Δ2/E
F
. At low energies ε≪ω
Th∼ (ω
0/τ)1/2, the energy level statistics is described by the “zero-dimensional” limit of this supermatrix theory, and the result for
the density of states is equivalent to that obtained within Altland-Zirnbauer random matrix model. Nonzero modes of the sigma
model increase the mean interlevel distance by the relative amount [2 ln (1/ω
0
τ)]−1.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 1, 78–83 (10 July 1998)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
8.
T. Mercouris C.A. Nicolaides 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(2):241-248
By implementing a time-independent, nonperturbative many-electron, many-photon theory (MEMPT), cycle-averaged complex eigenvalues
were obtained for the He atom, whose real part gives the field-induced energy shift, Δ(ω
1, F
1;ω
2, F
2,ϕ), and the imaginary part is the multiphoton ionization rate, Γ(ω
1, F
1;ω
2, F
2,ϕ), where ω is the frequency, F is the field strength and ϕ is the phase difference. Through analysis and computation we show that, provided the intensities
are weak, the dependence of Γ(ω
1, F
1;ω
2, F
2,ϕ) on ϕ is simple. Specifically, for odd harmonics, Γ varies linearly with cos(ϕ) whilst for even harmonics it varies linearly
with cos(2ϕ). In addition, this dependence on ϕ holds for Δ(ω
1, F
1;ω
2, F
2,ϕ) as well. These relations may turn out to be applicable to other atomic systems as well, and to provide a definition of
the weak field regime in the dichromatic case. When the combination of (ω
1, F
1) and (ω
2, F
2) is such that higher powers of cos(ϕ) and cos(2ϕ) become important, these rules break down and we reach the strong field
regime. The herein reported results refer to Γ(ω
1, F
1;ω
2, F
2,ϕ) and Δ(ω
1, F
1;ω
2, F
2,ϕ) for He irradiated by a dichromatic ac-field consisting of the fundamental wavelength λ = 248 nm and its 2nd, 3rd and 4th
higher harmonics. The intensities are in the range 1.0×1012-3.5×1014 W/cm2, with the intensity of the harmonics being 1-2 orders of magnitude smaller. The calculations incorporated systematically
electronic structure and electron correlation effects in the discrete and in the continuous spectrum, for 1S, 1P, 1D, 1F, 1G, and 1H two-electron states of even and odd parity.
Received 9 July 2000 and Received in final form 2 November 2000 相似文献
9.
A theory of the shift current induced by direct two-photon and indirect one-photon absorption is developed for noncentrosymmetric
crystals. A formula is derived for the microscopic shifts of Bloch electrons induced by two-quantum processes. It is shown
that the ratio of the two-photon photocurrent at the photon frequency ω to the photocurrent induced by direct one-photon transitions
at the photon frequency 2ω, as compared to the corresponding absorption-rate ratio, contains a large factor {ie152-1}ω/(2{ie152-2}ω
− E
g), where E
g is the bandgap; i.e., these photocurrent can be comparable in order of magnitude. For crystals of T
d
symmetry, the photocurrents induced by one- and two-photon absorption are compared in terms of polarization dependence. 相似文献
10.
E. Krotscheck R. E. Zillich 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):113-116
We present a microscopic theory and results of atom
scattering calculations to determine the dispersion of surface modes
(ripplons) of superfluid helium-4 nanodroplets, expanding previous
work [J. Chem. Phys. 115, 10161 (2001)]. A quantum transport formalism is
adapted to the many-body scattering problem, yielding both elastic and
inelastic fluxes. We demonstrate that, in analogy to the dynamic
structure function S(k,ω) obtained from neutron scattering, a
dynamic structure function σ(k,ω) can be obtained from
3He scattering. The 3He dynamic structure function
σ(k,ω) is sensitive to surface dynamics,
whereas the neutron dynamic structure function S(k,ω) is
dominated by bulk-like excitations, in particular by rotons.
Unlike for neutron-scattering, the total inelastic cross section for
atom-scattering on 4He nanodroplets is large which we believe makes
experimental detection feasible. We also show that scattering identical particles, i.e. 4He atoms, does not provide
information about the dispersion of surface modes. Instead,
inelastically scattered 4He atoms preferably lose roughly half
their energy. 相似文献
11.
M. S. Brodyn V. I. Volkov V. R. Lyakhovetskii V. I. Rudenko V. M. Puzilkov A. V. Semenov 《Journal of Experimental and Theoretical Physics》2012,114(2):205-211
The aim of this study is to investigate the nonlinearity of refraction in nanostructured silicon carbide films depending on
their structural features (synthesis conditions for such films, substrate temperature during their deposition, concentration
of the crystalline phase in the film, Si/C ratio of atomic concentrations in the film, and size of SiC nanocrystals formed
in the film). The corresponding dependences are obtained, as well as the values of nonlinear-optical third-order susceptibility
χ(3)(ω; ω, −ω, ω) for various silicon polytypes (3C, 21R, and 27R) which exceed the value of χ(3) in bulk silicon carbide single crystals by four orders of magnitude. 相似文献
12.
A. U. Sheleg V. G. Hurtavy S. N. Mustafaeva E. M. Kerimova 《Physics of the Solid State》2011,53(3):472-475
The temperature dependences of the electrical conductivity and the permittivity of TlInSe2 and TlGaTe2 crystals unirradiated and irradiated with 4-MeV electrons at a doze of 1016 cm−2 have been investigated. It has been established that electron irradiation leads to a decrease in the electrical conductivity
σ and the permittivity ɛ over the entire temperature range under study (90–320 K). It has been revealed that the TlInSe2 and TlGaTe2 single crystals undergo a sequence of phase transitions characteristic of crystals of this type, which manifest themselves
as anomalies in the temperature dependences σ = f(T) and ɛ = f(T). Electron irradiation at a doze of 1016 cm−2 does not affect the phase transition temperatures of the crystals under investigation. 相似文献
13.
V. A. Sadovnikova 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(7):905-907
We consider solutions of the zero sound dispersion equation in the standard model of random phase approximation. A method
for calculating solutions in the region of overlap between collective excitations and real particle-hole pairs is proposed.
The method takes advantage of the analytical structure of the polarization operator. The solutions of dispersion equation
with the full polarization operator Π(ω, k) and with the Re Π(ω, k) are compared. 相似文献
14.
A. Andreoni M. Bondani G.M. D'Ariano M.G.A. Paris 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(3):415-421
We propose a novel scheme for the joint generation of two squeezed beams at arbitrary frequencies ω
1 and ω
2. The scheme consists of two successive steps, both involving nonlinear interactions in χ(2) crystals. The dynamics of the setup is analyzed both quantum mechanically and classically within the parametric approximation.
An experimental implementation involving the fundamental and the harmonics of a Nd:YAG laser pulse, and β-BaB
2
O
4 nonlinear crystals is suggested.
Received 17 May 2000 and Received in final form 9 October 2000 相似文献
15.
An analytical expression I(ω) is obtained for a normalized function of the shape of an idealized nuclear quandrupole resonance
nutation line of a powdered sample for spins I=3/2 (η≠0). Calculations are made of the initial moments <ωn> of the nutation spectrum of the powder in the form of functions of ω0=γB1 and the asymmetry parameter η of the electric field gradient tensor. A method is proposed for determining the spectral parameters
η and eQqzz from the experimentally measured values of <ω>, <ω2>, <ω4>, and ω1/2 of the nuclear quadrupole resonance nutation spectrum of the powder.
State University, Kaliningrad. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 3–8, July, 1997. 相似文献
16.
Vl.A. Margulis S.V. Makarov T.V. Piterimova E.A. Gaiduk 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(2):153-164
Using a mean-field approximation, we have developed a systematic treatment of collective electronic modes in a semiconductor
superlattice (SL) in the presence of strong electric and magnetic fields parallel to the SL axis. The spectrum of collective
modes with zero wavevector along the SL axis is shown to consist of a principle magnetoplasmon mode and an infinite set of
Bernstein-like modes. For non-zero wavevector along the SL axis, in addition to the cyclotron modes, extra collective modes
are found at the frequencies |Nω
c±Mω
s|, which we call cyclotron-Stark modes (ω
c and ω
s are respectively the cyclotron and Stark frequencies, N and M are integer numbers). The frequencies of the modes propagating in “oblique” direction with respect to the SL axis show oscillatory
behavior as a function of electric field strength. All the modes considered have very weak spatial dispersion and they are
not Landau damped. The specific predictions made for the dispersion relations of the collective excitations should be observable
in resonant Raman scattering experiments.
Received 29 August 2002 / Received in final form 25 February 2003 Published online 4 June 2003
RID="a"
ID="a"e-mail: 612033@inbox.ru 相似文献
17.
M. R. Galpin D. E. Logan 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(2):129-145
We develop a non-perturbative local moment approach (LMA) for the gapped Anderson impurity model (GAIM), in which a locally
correlated orbital is coupled to a host with a gapped density of states.
Two distinct phases arise, separated by a level-crossing quantum phase transition: a screened singlet phase, adiabatically
connected to the non-interacting limit and as such a generalized Fermi liquid (GFL); and an incompletely screened, doubly
degenerate local moment (LM) phase.
On opening a gap (δ) in the host, the transition occurs at a critical gap δc, the GFL [LM] phase occurring for δ<δc [ δ>δc] . In agreement with numerical renormalization group (NRG) calculations, the critical
δc = 0 at the particle-hole symmetric point of the model, where the LM phase arises immediately on opening the gap. In the generic
case by contrast δc > 0, and the resultant LMA phase boundary is in good quantitative agreement with NRG results. Local single-particle dynamics
are considered in some detail.
The major difference between the two phases resides in bound states within the gap: the GFL phase is found to be characterised
by one bound state only, while the LM phase contains two such states straddling the chemical potential. Particular emphasis
is naturally given to the
strongly correlated, Kondo regime of the model. Here,
single-particle dynamics for both phases are found to exhibit universal scaling as a function of scaled frequency ω/ωm
0 for fixed gaps
δ/ωm
0, where ωm
0 is the characteristic Kondo scale for the gapless (metallic) AIM; at particle-hole symmetry in particular, the
scaling spectra are obtained in closed form. For frequencies
|ω|/ωm
0 ≫δ/ωm
0, the
scaling spectra are found generally to reduce to those of the gapless, metallic Anderson model;
such that for small gaps δ/ωm
0≪ 1 in particular, the Kondo resonance that is the spectral hallmark of the usual metallic Anderson model persists more or
less in its entirety in the GAIM. 相似文献
18.
Suleyman Cabuk 《Central European Journal of Physics》2012,10(1):239-252
The nonlinear optical properties of some ABO3 materials (BaTiO3, KNbO3, LiTaO3 and LiNbO3) are studied by density functional theory (DFT) in the local density approximation (LDA) expressions based on first-principle
calculations. Our goals are to give the details of the calculations for linear and nonlinear optical properties, including
the linear electro-optic (EO) tensor for some ABO3 structures with oxygen octahedral structures using first-principles methods. These results can then be used in the study
of the physics of ferroelectrics, specifically, we present calculations of the second harmonic generation response coefficient
X
ijk
(2) (−2ω, ω, ω) over a large frequency range for ABO3 crystals. The electronic linear EO susceptibility X
ijk
(2) (−ω, ω,0) is also evaluated below the band gap. These results are based on a series of the LDA calculations using DFT. Results for
X
ijk
(2) (−ω, ω,0) are in agreement with experiments below the band gap. The results are compared with the theoretical calculations and the
available experimental data. 相似文献
19.
L. V. Nomerovannaya A. A. Makhnëv A. Yu. Rumyantsev 《Physics of the Solid State》1999,41(8):1322-1326
An ellipsometric method is used to study the dispersion of the real ɛ
1(ω) and imaginary ɛ
2(ω) parts of the complex dielectric permittivity of single-crystal La1−x
SrxMnO3 (x=0.1, 0.2, and 0.3) for energies from 100 meV to 5 eV at room temperature. It is found that, when lanthanum is replaced by
strontium, the optical spectrum changes fundamentally. A shift in the main features of the spectrum of initial LaMnO3 at 1.9 and 4.7 eV to lower energies takes place, as well as a partial redistribution of the optical-conductivity spectral
weight in the band gap region E<1.7 eV. For compositions with x=0.2 and 0.3, a fine structure of the interband absorption is observed against a background of non-Drude optical conductivity
at low energies.
Fiz. Tverd. Tela (St. Petersburg) 41, 1445–1449 (August 1999) 相似文献
20.
Nonreciprocal birefringence due to magnetically induced spatial dispersion was observed in the T
d-class cubic semiconductors ZnTe, CdTe, and GaAs near the fundamental absorption edge. The dispersion of the parameters A and g, describing the contributions from terms of the type B
ikj to the diagonal and off-diagonal components of the permittivity tensor ε
ij(ω,B,k), is determined for ZnTe and CdTe. Analysis of the dispersion and anisotropy of the nonreciprocal birefringence shows that
in ZnTe, CdTe, and GaAs, in contrast to magnetic semiconductors of the type Cd1−x
MnxTe, it is due excitonic mechanisms.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 7, 514–519 (10 April 1999) 相似文献