共查询到20条相似文献,搜索用时 46 毫秒
1.
Pradeep Kumar 《Phase Transitions》2015,88(6):605-620
A comparative study of two different particle sizes of ferroelectric barium titanate (BaTiO3) nanoparticles as a dopant on the molecular structure, spontaneous polarization and dielectric behavior of a pure ferroelectric liquid crystal 6F6T have been studied. It has been found that there is a remarkable decrease in isotropic temperature of both doped samples as compared to the pure 6F6T sample. The spontaneous polarization also decreases for both the doped samples and the reduction is more pronounced in case of the dopant with large particle size. The dielectric spectroscopy confirms the presence of soft mode as well as Goldstone mode and also shows the decrease in the value of dielectric permittivity ?' as a function of frequency for both doped samples. The improvised properties of liquid crystal host doped with BaTiO3 nanoparticles mainly depend upon the synthesis method of nanoparticles and also upon the particle size of dopant. 相似文献
2.
S. G. Karshenboim 《Journal of Experimental and Theoretical Physics》1999,89(5):850-855
This paper examines the shift of energy levels in a hydrogenlike atom induced by vacuum polarization effects. The contribution
of free polarization is found for the ground state and several excited states in a closed analytical form. For the first time
an expression is derived for the radiative correction to the energy in the form of an explicit function of the parameter Zα. The results are valid for states nl
j with the largest values of orbital and total angular momenta (l=n−1 and j=l+1/2). The final expression, found in terms of generalized hypergeometric functions, is a function of three variables, Zα, n, and the ratio of the particle masses on the orbit and in the vacuum loop, i.e., the result is valid for ordinary atoms and
for muonic atoms. Several useful asymptotic expressions are also derived.
Zh. éksp. Teor. Fiz. 116, 1575–1586 (November 1999) 相似文献
3.
A nuclear matter test has been conducted on a separable non-localN-N interaction proposed by Sirohi and Srivastava. The potential had been constructed by fitting the phase-shifts. The results
obtained compare with those obtained by Tabakin in each partial wave. The binding energy per particle and the symmetry energy
coefficient obtained are 19.4 MeV and 66.5 MeV respectively atk
F=1.65 fm−1, while the best estimated values for these quantities are 16 MeV and 30–35 MeV atk
F=1.5 fm−1. Single particle potential generated out of this NLSI has in general the same shape as the one obtained through Tabakin potential.
Finally as a test of non-locality the integrated photoabsorption cross-section parameterh has been calculated and the value of 1.03 agrees with other reported values. 相似文献
4.
利用密度矩阵重整化群(DMRG)方法研究磁性阻挫对一种S=1/2准一维反铁磁自旋链但却具有亚铁磁性的Heisenberg系统基态的影响.计算了单个晶胞的基态能、自旋关联函数以及自旋能隙.研究表明这种Heisenberg自旋系统的基态随着阻挫α的增强将从磁有序相变化到自旋无序相,并且伴随着自旋能隙的出现,量子相变点为α≈0.412.同时线形链上格点间自旋长程关联值的计算结果表明在磁有序区间体系的磁有序性质随着α的增强而减弱,阻挫在0≤α<
关键词:
准一维反铁磁自旋链
亚铁磁性
密度矩阵重整化群
自旋能隙 相似文献
5.
Mario Rabinowitz 《International Journal of Theoretical Physics》1989,28(2):137-146
A quantum mechanical model requiring only strong quantum interaction for a charged particle gas estimates the superconducting transition temperature for wide-ranging states of matter. A general equation is derived which estimates the critical temperatureT
c
the energy gap, and the coherence length for the classical metallic superconductors, heavy-electron superconductors, the perovskites, metallic hydrogen, and neutron stars. Estimates forT
c
, the coherence length, and the energy gap which are model independent for coupling mechanisms agree well with accepted values for these materials. Estimates are made for threedimensional quasi-two and quasi-one-dimensional states. 相似文献
6.
在单电子紧束缚近似下,建立了准一维多链无序体系直流、交流电子跳跃输运模型,通过计算探讨了无序模式、维度效应、温度及外场对其直流、交流电导率的影响.计算结果表明:准一维多链无序体系的直流、交流电导率随着格点能量无序度的增大而减小,非对角无序具有增强体系电子输运能力的作用.随着链数的增加,体系的直流、交流电导率增大,但格点能量无序度较小时,维度效应的影响不明显.在对角无序情况下准一维多链无序体系的交流电导率随温度的升高而增大,而在非对角无序模式下却随温度的升高而减小,但对于直流情况,体系的直流电导率随温度的升 相似文献
7.
A. A. Sinchenko Yu. I. Latyshev S. G. Zybtsev I. G. Gorlova P. Monceau 《JETP Letters》1996,64(4):285-291
Nonlinear effects at the interface between a normal metal and the quasi-one-dimensional conductor with a charge-density wave
K0.3MoO3 are investigated experimentally. It is found that the scattering of the normal carriers with energy E less than the Peierls gap Δp gives rise to an excess resistance of the N-CDW boundary. The character of the scattering is similar to Andreev reflection.
In contrast to superconductors, however, the sign of the charge of the reflected particle does not change.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 4, 259–264 (25 August 1996) 相似文献
8.
S. S. Gavrilov N. A. Gippius S. G. Tikhodeev V. D. Kulakovskii 《Journal of Experimental and Theoretical Physics》2010,110(5):825-836
The nonlinear dynamic properties of a system of polaritons in a planar semiconductor microcavity under conditions of external
coherent photoexcitation have been investigated. It has been shown that the interaction between polaritons with identical
projections of the total angular momentum (J
z
) can give rise to multistability of the response of the excited polariton state. As a result, nonequilibrium transitions
between different stability branches become possible due to fluctuations or arbitrarily smooth variations of the excitation
parameters and occur with abrupt changes in the intensity and optical polarization of the field in the microcavity. It has
been demonstrated that a relatively weak attraction between polaritons with opposite total angular momenta J
z
leads to a possibility of spontaneously breaking the symmetry of circularly polarized field components in the microcavity
under strictly linear (symmetric) polarization conditions of external excitation. 相似文献
9.
Yu. I. Bogdanov R. F. Galeev S. P. Kulik G. A. Maslennikov E. V. Moreva 《JETP Letters》2005,82(3):164-168
A method for reconstructing an arbitrary quantum state of an optical system in Hilbert space with dimension d = 4 is discussed. Such states can be realized using a collinear frequency-nondegenerate regime of generating spontaneous parametric down-conversion. The method has been tested for a number of polarization states of a biphoton field. The high accuracy of the reconstruction of the states (above 99%) indicates that the procedures proposed for reconstructing the quantum state of the system are adequate. 相似文献
10.
11.
The salient features of the total low energy inelastic electron scattering cross section in transition metals are described by a constant term σ0 plus a term σd that is proportional to the number of unoccupied d-orbitals. This simple model predicts that low energy electrons transmitted through a ferromagnetic ultrathin film acquire a transport spin polarization a(χ). Using the ratio σ0/σd as the only adjustable parameter, the model predicts the enhancement of the spin polarization of the low energy cascade electrons as well as a(χ) in reasonable agreement with the existing observations on Fe, Co and Ni. A detector for electron spin polarization P based on the spin dependent transmission of electrons through ferromagnetic material is proposed which should be superior to existing P-detectors by 1–2 orders of magnitude. 相似文献
12.
A. V. Golenishchev-Kutuzov V. A. Golenishchev-Kutuzov R. I. Kalimullin A. A. Potapov 《Physics of the Solid State》2011,53(3):518-521
Variations in local polarization switching fields E
C
in lithium niobate crystals have been investigated under laser irradiation of the z surface. It has been established that the simultaneous application of an electric field in the direction opposite to the
spontaneous polarization field and laser beam leads to a decrease in the field E
C
. 相似文献
13.
S. Santhosh Kumar 《Pramana》2008,71(1):175-180
In the present calculation we have used the Monte Carlo method of generating collective spin and total energy of the nucleus
for various configurations of the system with N
0 single particle states available for n number of particles. The different configurations (arrangements of occupied single particle states) leading to a particular
energy E and spin J are then collected to get the density of states for the given energy E and spin J. We find that if we use the cranked Nilsson model single particle states for the rotational frequency Ω = 0.0ħω, 0.05ħω and 0.1ħω there is a shift in the maximum density of states W
max with a tendency for the system to become more oblate or prolate depending on the shift in the maximum density of states as
the angular momentum decreases or increases. The change in nuclear level density with collectivity, i.e. with the use of cranked
Nilsson model single particle levels has been noticed.
相似文献
14.
O. Kreitschitz W. Husinsky G. Betz N. H. Tolk 《Applied Physics A: Materials Science & Processing》1994,58(6):563-571
The intensity dependence of the total and specific yields of positive ions desorbed from SrF2 under 193 nm and 308 nm excimer-laser irradiation has been investigated by the time-of-flight method. The following positive ion species have been detected: F+, Sr+, Sr++, SrF++ and SrF
2
+
. The Sr+ and SrF+ emission yields are found to increase as E
n, where E represents the laser energy per pulse. The exponent n is related to defect-initiated neutral particle emission and gas-phase ionization. The influence of surface damage on this power dependence is investigated. The F+ emission yield showed a quite different behaviour compared to that of the Sr+ and SrF+ emission. At both wavelengths the total positive ion emission yields saturate at a certain laser energy. In the saturation regime the SrF+ emission vanishes and alternative emission of F+ and Sr+ was observed at both wavelengths, but the total emission yield in the saturation regime (F+ + Sr+) remained constant. A Scanning Electron Microscope (SEM) was used to investigate the damage spots after laser irradiation for thermal effects. 相似文献
15.
In this work the effects of magnetoelastic interaction in Rare-Earth compounds between excited crystal field states and nondegenerate optical phonons have been studied in tetragonal TmVO4 and in orthorhombic TbF3, using Raman and far-infrared spectroscopy. In certain favourable cases a mutual energy renormalization of the phonons has been observed as a function of a magnetic field (TmVO4) or depending on the direction of the spontaneous magnetization of the crystal (TbF3).In magnetically ordered TbF3 an effective phonon-phonon coupling between modes of pure transverse and longitudinal polarization has been studied. This interaction results in an elliptical polarization of the coupled polar modes and transfers transition intensity to the quasi-longitudinal modes.The observed phenomena have been treated theoretically in full agreement with the experiments as higher order effects using the well established theory of magnetoelastic effects. 相似文献
16.
Effects of magnetic ordering associated with the Coulomb exchange interaction of free electrons in a 2D Fermi system are considered.
It is shown that the paramagnetic response is substantially enhanced by Fermi-liquid effects. The phase transition to a state
with spontaneous polarization of spins can be observed when Heisenberg parameter J is not smaller than μF/3.06 (approximately one-third of the Fermi energy) and not larger than half the Fermi energy (J ≤ μF/2). 相似文献
17.
A well-formed energy gap Δ is observed in the energy spectrum of the quasi-one-dimensional orthorhombic conductor TaS3 at temperatures much lower than the Peierls transition temperature T
P
. As the temperature increases, in the region T>T
P
/2 there is a growth of the density of states in the gap and a relative decrease of the density at energies greater than Δ.
In addition, absorption lines which probably correspond to soliton states in a charge-density wave are observed in the gap.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 4, 246–250 (25 February 1996) 相似文献
18.
Shigeki Ohsugi Yoshio Kitaoka Masaki Azuma Yoshie Fujishiro Mikio Takano Takashi Nagata Hirokazu Fujino Jun Akimitsu 《Hyperfine Interactions》2001,133(1-4):157-162
Cu nuclear magnetic resonance (NMR) spectra of impurities (Zn, Ni, and La)-doped spin-1/2 Heisenberg ladder compounds SrCu2O3 (Sr123) are broadened with Curie-like temperature (T) dependence. The spectra have been successfully fit by using a quasi-one-dimensional (Q1D) staggered polarization (SP) model. Such a SP has also revealed in Cu NMR measurements of Sr14–x
Ca
x
Cu24O41 (Cax) with hole-doped ladders. The origin of possible 3D antiferromagnetic (AF) long-range ordering in (Zn and Ni)-doped Sr123 and Cax around x=12 at low T is considered to be similar. Once unpaired spins S
0's are induced and 3D interlayer interaction occurs, the localized spins couple in the whole system. 相似文献
19.
Collision induced non-radiative transitions in neon plasma have been studied using high intra-cavity radiation field of a
633 nm He-Ne laser. The transitions, induced from 3s
2 energy level to 4s1 and 5s1 groups of energy levels, have been detected as changes in intensities of the spectral lines originating from these energy
levels. From these intensity measurements, the quantities governing the transitions i.e. (i)S
3
e
/S
3RT
, the ratio of the probabilities of electronic deexcitation to the total radiative deexcitation of energy level 3 (ii) 〈r
23
e
v
e〉, rate of excitation transfer per particle and (iii)S
23
e
, the total probability for excitation transfer from level 2 to level 3 at a certain value of electron density have been calculated. 相似文献
20.
Gunyakov VA Parshin AM Shabanov VF 《The European physical journal. E, Soft matter》2006,20(4):467-473
Specific features of the anisotropic interaction between a nematic mixture and a polar surface of a ferroelectric triglycine
sulfate crystal have been studied over a wide temperature range including the substrate's Curie point Tc. The mixture was composed of two nematic liquid crystals, 60% of p-methoxybenzylidene-p-n-butylaniline (MBBA) and 40% of p-ethoxybenzylidene-p-n-butylaniline (EBBA), and doped with a small amount of a dichroic dye. The temperature dependence of the polarized components
of optical density Dj of the dye absorption band for the nematic and isotropic phases of the MBBA+EBBA mixture has been obtained using polarization
optic techniques. The temperature-induced structural changes in the nematic layer near Tc were found to be related to the changes in the orientational part of the tensor order parameter Qik. The experimental data have been interpreted using the model, in which the dispersive van der Waals forces of the substrate
stabilize the planar orientation of the nematic in the bulk competing with the short-range anchoring forces in the vicinity
of Tc. At the same time, the anisotropic part of the surface energy has two terms with the orthogonal easy axes. The nature of
the surface electric field and its effect on the director alignment at the interface have been clarified. Taking into account
the known relation between anchoring strength and the nematic order parameter, the effective anchoring energy weff for the studied system has been determined as a function of temperature. 相似文献