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1.
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
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采用交叉色关联的加性色噪声和乘性色噪声驱动的单模激光立方模型,通过诺维科夫理论和福克斯近似以及斯特拉托诺维奇近似,得到反映激光统计性质的强度关联函数C的表达式;研究关联时间τ、净增益系数a0和交叉关联强度λ对强度关联函数C的影响.数值模拟发现,在阈值以上(a0>0)时,关联函数C随关联时间τ的增大而增大;在阈值以下(a0<0)时,关联函数C随关联时间τ的增大而减小.无论在阈值以上还是阈值以下,关联函数C均随交叉关联强度λ的增大而减小.在C-a0曲线上存在单峰.
关键词:
单模激光
交叉关联
强度涨落
强度关联函数 相似文献
6.
研究了一维三量子比特海森伯模型中的对纠缠的提高和控制问题,在该系统中引入了Dzyaloshinskii-Moriya(DM)相互作用,通过求解共生来计算两量子比特之间的热纠缠,结果表明:对于XXX模型,引入DM相互作用D,可以诱导铁磁和反铁磁自旋链产生热纠缠,尽管它们产生热纠缠所需的D值大小不同.对于XXZ模型,引入DM相互作用后,可以使原本不存在热纠缠的反铁磁自旋链产生纠缠,而且对于铁磁和反铁磁这两种XXZ自旋链,DM相互作用和各向异
关键词:
纠缠
XXX模型')" href="#">XXX模型
XXZ模型')" href="#">XXZ模型
Dzyaloshinskii-Moriya相互作用 相似文献
7.
讨论考虑洪特耦合的两带赫伯德模型得到的一维自旋轨道模型中自旋-轨道能隙的产生.运用SU(4)赝费米子表象下的平均场理论,计算求得价键序参数、准粒子激发谱能隙和自旋、轨道密度-密度关联函数随系统耦合参数变化的结果.随洪特耦合相互作用由零开始增强,系统激发谱能隙逐渐打开,并且系统在参数取值为J1/J2=1/3处由具有阻错的无序状态相变到自旋铁磁有序和轨道反铁磁有序的状态. 相似文献
8.
将角通量分解成一个δ函数和一个低阶函数,分别采用解析方法和求积组来计算源项.利用δ函数SN方法,计算了平几何条件下含各向异性散射单速输运方程的临界问题.分析和数值结果表明,采用数量较少的离散方向,能够达到较高计算精度. 相似文献
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本文以反铁磁海森伯模型为对象,设想了一个相互作用在t=0时刻开启的非平衡体系.在低温近似下,本文利用重整化群流方程方法讨论了该体系可观测量随时间的演化趋势.本文根据此类体系的特点,给出了获得算符时间演化形式的路径,并成功将其应用于本文所讨论的模型中.其中,本文着重介绍了如何在非平衡自旋体系中应用流方程方法,并利用该方法得到了随时间演化的基态磁化强度,同时论证了该方法处理此类系统的有效性.同时,在与平衡体系基态磁化强度的对比中,发现非平衡可观测量随时间震荡而无法收敛,这一点有别于相互作用突然开
关键词:
非平衡体系
反铁磁海森伯模型
流方程方法
磁化强度 相似文献
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Molecular dynamics simulations of water, liquid beryllium fluoride and silica melt are used to study the accuracy with which the entropy of ionic and molecular liquids can be estimated from atom–atom radial distribution function data. The pair correlation entropy is demonstrated to be sufficiently accurate that the density–temperature regime of anomalous behaviour as well as the strength of the entropy anomaly can be predicted reliably for both ionic melts as well as different rigid-body pair potentials for water. Errors in the total thermodynamic entropy for ionic melts due to the pair correlation approximation are of the order of 10% or less for most state points, but can be significantly larger in the anomalous regime at very low temperatures. In the case of water, the rigid-body constraints result in larger errors in the pair correlation approximation, between 20 and 30%, for most state points. Comparison of the excess entropy, S e, of ionic melts with the pair correlation entropy, S 2, shows that the temperature dependence of S e is well described by T ?2/5 scaling across both the normal and anomalous regimes, unlike in the case of S 2. The residual multiparticle entropy, ΔS = S e ? S 2, shows a strong negative correlation with tetrahedral order in the anomalous regime. 相似文献
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Scattering on molecules, correlated in regions of short-range quasi-ordering, is analysed with regard to its effect on the spectrum of hyper-Rayleigh light-scattering by molecular liquids. The general form of S 2ω c(?, Δω) derived using spherical tensors and expanding the orientational-positional-time pair correlation function in Wigner functions, is discussed on the assumption that Vineyard's [22] approximation can be applied to calculate G c[τ1(t), τ2(0)]. Successive terms of the expansion are calculated assuming dipole-dipole interaction energy as predominant in the total molecular electric multipole interaction energy. In the present approximation the contribution from scattering on correlated molecules is shown to be given by the difference of two Lorentz lines, whose maxima depend on the magnitude of the interactions. The integral intensities, calculated from the formulae derived here, are in agreement with those of the literature. 相似文献
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采用全相对论扭曲波方法,系统地计算了类铍N3+和 O4+离子从基态到2s2p和2p2 的各激发态以及从亚稳态到2p2各激发态的电子碰撞激发截面,详细地讨论了靶态的关联效应对激发截面的影响.结果表明:对于2s-2p的单电子激发,在低能碰撞时,靶态的电子关联效应起非常重要的作用,且使得激发截面降低;而高能碰撞时,靶态波函数的描述对连续态波函数的影响比较小,对激发截面影响也比较小.对于2s2-2p2的双电子激发,其中基态2s21S0到J=0的2p23P0,1S0的激发截面较大,其主要原因是末离子态波函数与基组态波函数的混合,但是其他几个激发的激发截面较小.
关键词:
全相对论扭曲波方法
电子碰撞激发
电子关联效应 相似文献
14.
The total (p, n) reaction cross section for48Ca has been measured as a function of proton energy in the energy range 1.885 to 5.100 MeV with an overall resolution of ∼
2 keV and in ∼ 5 keV energy steps. The fluctutions in fine resolution data have been analysed to determine the average coherence
width 〈Γ〉. The excitation function averaged over large energy intervals has been analyzed in terms of the optical model. The
isobaric analogue resonances atE
p
∼ 1.95 and 4 MeV have been shape-analyzed to extract the proton partial width and the spectroscopic factorS
n
. A comparison of the gross structures observed in ∼ 55 keV averaged excitation function with the predictions of Izumo’s partial
equilibrium model has also been made. 相似文献
15.
The vibronic coupling between the first excited S1 (21Ag) and the second excited S2 (11Bu) singlet electronic states in spectroscopy of trans‐1,3,5‐hexatriene molecule is investigated on the basis of a model consisting of two electronic states coupled by two vibrational modes. Employing a perturbation theory that treats the intramolecular couplings in a perturbative manner, the absorption and resonance Raman cross sections and excitation profiles of this molecule are calculated using the time‐correlation function formalism. The non‐Condon corrections are included in evaluation of cross sections. The multidimensional time‐domain integrals that arise in these calculations have been evaluated for the case in which S0 (11Ag) S2 (11Bu) electronic transition takes place between displaced and distorted harmonic potential energy surfaces. The calculated spectra are in good agreement with the experimental ones. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
16.
M. S. Rasheedy 《辐射效应与固体损伤》2013,168(9):383-390
The Hoogenstraaten method is a technique that uses various heating rates for obtaining the activation energy E (eV) in the case of first-order thermoluminescence glow peaks. This method can also be used for obtaining E (eV) for all types of glow peaks regardless of their kinetics order (b). The present work shows that the intercept of the Hoogenstraaten relation, which is usually used for obtaining the frequency factor S (s ?1) of the first-order glow peak, can be used as a very good approximation to obtain the pre-exponential factor S ′ ′ (s ?1) in the case of general-order glow peaks, when one uses Hoogenstraaten’s method to obtain E (eV). In addition, the present work suggests a numerical method for obtaining the kinetics order of the general-order glow peak. The method depends on the activation energy E (eV) obtained by the Hoogenstraaten method and the above-mentioned approximation for obtaining the pre-exponential factor S ′ ′ (s ?1). An independent evaluation of the suggested methods for obtaining the trap parameters, the activation energy E (eV), the pre-exponential factor S ′ ′ (s ?1) and the kinetics order (b) is illustrated here by taking a numerically computed glow peak and applying a one-trap and one-recombination-center model. 相似文献
17.
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
18.
We derive the exact expression of the four-spinon contribution S
4 to the dynamical correlation function S of the spin 1/2 isotropic (XXX) He isenberg model in the antiferromagnetic regime using the quantum group symmetry of the
model. We first give the exact expression for the n-spinon contribution in the form of contour integrals and display known results regarding the two-spinon contribution S
2. Then we specialize the n-spinon formula to the case n = 4 and compute three sum rules for S
4 that the total S is known to satisfy exactly. These are: the total integrated intensity, the first frequency moment and the nearest-neighbor
correlation function. We find that S
4 corrects only by a small amount the contribution from S
2.
Presented at the International Colloquium “Integrable Systems and Quantum Symmetries”, Prague, 16–18 June 2005. 相似文献
19.
Energy and momentum of general spherically symmetric frames on the regularizing teleparallelism 下载免费PDF全文
Gamal G. L. Nashed 《中国物理 B》2012,21(1):10401-010401
In the context of the covariant teleparallel framework, we use the 2-form translational momentum to compute the total energy of two general spherically symmetric frames. The first one is characterized by an arbitrary function H(r), which preserves the spherical symmetry and reproduces all the previous solutions, while the other one is characterized by a parameter ξ which ensures the vanishing of the axial of trace of the torsion. We calculate the total energy by using two procedures, i.e., when the Weitzenböck connection Γαβ is trivial, and show how H(r) and ξ play the role of an inertia that leads the total energy to be unphysical. Therefore, we take into account Γαβ and show that although the space×we use contain an arbitrary function and one parameter, they have no effect on the form of the total energy and momentum as it should be. 相似文献
20.
Properties of semi-infinite (S=1) Heisenberg ferromagnet with biquadratic exchange were studied in terms of surface exchange (=IS/I) and biquadratic coupling (a). It was shown that a strict correlation exists, depending on , between the type of surface spin waves (acoustic or optical) and the mean-field (MF) critical temperature, bulk (Tc) and surface TcS>Tc (for
). Within the framework of the Landau–Ginsburg theory for semi-infinite simple cubic ferromagnet, a detailed study is presented of the critical behaviour of the system, in particular in the vicinity of the tricritical point which is the consequence of the biquadratic interaction. It is shown that tricritical exponents satisfy exactly the scaling relations for d=3. The analysis of the spin–spin correlation function within the framework of the same theory, shows that there occurs the critical magnetic scattering of low-energy electrons (LEED) from the surface in the case
, when the ordering temperature TcS is approached from above (from paramagnetic phase). In the opposite case,
, there occurs no surface critical scattering. It was also shown that in the vicinity of the tricritical point, the biquadratic interaction increases the range of validity of the MF approximation. 相似文献