Coherence and squeezing in Z3‐graded spin coherent states

A new kind of spin coherent state called a Z₃‐graded spin coherent state is constructed by using the complex solution of the equation q³ = 1. We explicitly find three kinds of Z₃‐graded spin coherent states. The associated coherent property and spin squeezing are also examined.     

Josephson current versus potential strength of the interface in ferromagnetic superconductors

Based on the scattering theory, we calculate the Josephson current in a junction between two ferromagnetic superconductors as a function of the interface potential z. We consider the ferromagnetic superconductor(FS) in three different Cooper pairing states: spin singlet s-wave pairing(SWP) state, spin triplet opposite spin pairing(OSP) state, and spin triplet equal spin pairing(ESP) state. We find that the critical Josephson current as a function of z shows clear differences among the SWP, OSP, and ESP states. The obtained results can be used as a useful tool for determining the pair symmetry of the ferromagnetic superconductors.     

Using resonance Raman cross‐section data to estimate the spin‐state populations of cytochromes P450

The cytochromes P450 (CYPs) are heme proteins responsible for the oxidation of xenobiotics and pharmaceuticals and the biosynthesis of essential steroid products. In all cases, substrate binding initiates the enzymatic cycle, converting ferric low‐spin to high‐spin state, with the efficiency of the conversion varying widely for different substrates, so documentation of this conversion for a given substrate is an important objective. Resonance Raman (rR) spectroscopy can effectively yield distinctive frequencies for the ν₃ ‘spin state marker’ bands. Here, employing a reference cytochrome P450 (CYP101), the intensities of the ν₃ modes (I_LS) and (I_HS) relative to an internal standard (sodium sulfate) yield relative populations for the two spin states; i.e., a value of 1.24 was determined for the ratio of the relative cross sections for the ν₃ modes. The use of this value was then shown to permit a reliable calculation of relative populations of the two spin states from rR spectra of several other CYPs P450. The importance of this work is that, using this information, it is now possible to conveniently document by rR the spin state population without conducting separate experiments requiring different analytical methods, instrumentation, and additional sample. Copyright © 2013 John Wiley & Sons, Ltd.     

自旋电子学和相干态

自旋电子学是近年来发展起来的一个新研究领域,它研究固体,特别是半导体中的电子自旋相干态,实验发现,自旋相干态能够保持足够长的时间（几百ps量级）,因此有可能用来制造一个固态的量子计算机,但是制造实际的自旋电子器件,首先需要解决的是将自旋极化电子（或穴穴）注入半导体中的方法和如何检测它们。     

固体中半整数四极核的自旋扩散

首先介绍固态中自旋扩散的一般理论，包括半经典描述和建立在投影算子理论上的密度矩阵描述. 接着以丰核环境中相互偶合的自旋-1/2系统以及自旋-3/2系统为典型列举了自旋扩散速率的计算. 最近藉助多量子魔角旋转(MQMAS)方法实现半整数四极核的多量子谱自旋扩散实验，可以测量固体粉末中半整数四极核体系四极张量相对方向. 结合作者最近的计算机模拟和实验测量结果对这一新兴方向作了重点介绍，尤其指出了射频
脉冲强度、宽度及样品旋转速度对交叉峰线型的影响.     

Lower hybrid wave instability in a spin‐polarized degenerate plasma

Lower hybrid (LH) wave instability excited due to an electron beam in a spin‐polarized degenerate plasma is studied. Using the Separate Spin Evolution quantum hydrodynamic model, incorporating Coulomb exchange interaction and Bohm potential, the general dispersion relation of nearly perpendicular propagating electrostatic waves is derived. Furthermore, in the low‐frequency limit, the dispersion of LH wave is obtained. It is found that the electron spin polarization and beam streaming speed reduce the growth rate as well as the k‐domain. However, the beam density and the propagation angle enhance both the growth rate and k‐domain of LH instability. In addition, the contribution of the Bohm potential term increases the intensity of the growth rate. All these effects may have a strong bearing on the wave and instability phenomena in spin‐polarized plasmas.     

Origin of Spin Wave Gap in Metallic Ferromagnet La1-χAχMnO3

The spin wave spectrum of the double-exchange model with anisotropic Hund coupling is investigated using the spin wave approximation and Green's function approach based on Furukawa's work [J. Phys. Soc. Jpn. 65 (1996) 1174]. It is found that there exists a spin gap, which agrees with the observations in the inelastic neutron scattering experiments for La_0.7Sr_0.3MnO₃ and La_0.7Pb_0.3MnO₃. The spin gap is directly related to the anisotropy of Hund coupling. The ratio of the xy and z Hund coupling strengths is estimated from experimental data and the possible origin of the spin gap from the Jahn-Teller effect is pointed out.     

制备三量子位和四量子位核磁共振等效纯态

基于时间平均法,给出了在同核系统中制备三量子位和四量子位核磁共振等效纯态的方案.利用Λn(not)门,本文的方案大大减少了制备等效纯态所需的操作次数:在三同核系统中制备三量子位核磁共振等效纯态只需三次操作,在四同核系统中制备四量子位核磁共振等效纯态只需五次操作.然后在一个链状耦合的同核系统中实验制备三量子位核磁共振等效纯态,验证了本文的方案 并且给出了四量子位方案的模拟结果谱图     

Spin-3/2 Ising model AFM/AFM two-layer lattice with crystal field

The spin-3/2 Ising model is investigated for the case of antiferromagnetic (AFM/AFM) interactions on the two-layer Bethe lattice by using the exact recursion relations in the pairwise approach for given coordination numbers q=3, 4 and 6 when the layers are under the influences of equal external magnetic and equal crystal fields. The ground state (GS) phase diagrams are obtained on the different planes in detail and then the temperature-dependent phase diagrams of the system are calculated accordingly. It is observed that the system presents both second- and first-order phase transitions for all q, therefore, tricritical points. It is also found that the system exhibits double-critical end points and isolated points. The model also presents two Néel temperatures, T_N, and the existence of which leads to the reentrant behaviour.     

139Ce的多准粒子激发态

利用能量为50MeV的¹²C束流, 通过反应¹³⁰Te(¹²C,3n)布居了¹³⁹Ce的高自旋态. 基于标准在束核谱学实验测量结果, 扩展并更新了¹³⁹Ce的能级纲图. ¹³⁹Ce的能级结构具有球形原子核的典型特征, 其高自旋态由单粒子激发形成. 利用经验壳模型计算了¹³⁹Ce的多准粒子激发态能量, 研究了其高自旋激发态的多准粒子特性.     

磁性物质交换Hamiltonian中两项的竞争

对于一个N电子体系, 正确的交换Hamilton应该由两项组成，为H_ex=-2A1ii·s_j-2A₂ii·sj，而不是以往的铁磁学理论使用的H_ex=-2Aii ·s_j （其中A为A₁与A₂的代数和， A₁>0, A₂<0）, 以往的理论使用了一个不合理的交换Hamiltonian量.-2A₁ii·s_j与-2A₂ii< /sub>·s_j在数学上是同类项，但是在物理上不是 同类项，它们有不同的本征态和本征值.根据量子力学中的态叠加原理，这个电子系统的本 征态矢为X〉=1A²₁+A²₂(A₁ 1〉+A₂‖2〉),其中Dirac符号1〉表示系统所有电子 的自旋平行排列时的态（简称平行自旋态）矢量，2〉表示系统所有电子或最近邻电子的自 旋反平行排列时的态（简称反平行自旋态）矢量，H_ex的本征值（即系统的 交换能） 为E=-Nz（A₁-A₂）-2NzA₂²A₁ +A₂=-Nz（A₂-A₁）-2NzA²₁A< sub>1+A₂,其中z为最近邻电子数.当A₂=0时，X〉=1〉，E =-A₁, 系统具有Wei ss 铁磁性；当A₁ =0 时，X〉=2〉，E =-A₂，系统具有Neel 反铁磁性；当A₁ =A₂（即A=0）时，X〉=12 (1〉+2〉)，E=-A₁，系统处于自旋玻璃（spin glass）态；当A₁>A ₂时，X〉=1A²₁+A²₂［(A₁-A₂)1〉+A₂(1〉+2〉)］,平行自旋态与自旋 玻璃态共存；当A₁2时，X〉=1A²₁+A2₂［(A₂-A₁)2〉+A₁( 1〉+2〉)］，反平行自旋态与自旋玻 璃态共存.与原来理论中的Weiss铁磁态或Neel反铁磁态相比，平行自旋态与自旋玻璃态共存 或反平行自旋态与自旋玻璃态共存使系统的交换能降低.自旋玻璃态中电子自旋之间取向的 随机性或无序性是由交换Hamiltonian中-2A₁iis_j与-2A₂ii·s_j之间的竞争引起的，不是热运 动引起的. 关键词： 交换哈密顿量 铁磁态 反铁磁态 自旋玻璃态     

整数自旋协变波函数

对高自旋态的Bargmann-Wigner方程的解进行了改造,给出了一套系统地构造高自旋态(整数自旋)协变波函数的新方法.利用这种方法,分别构造了任意整数自旋粒子的协变波函数.     

The spin evolution of spin-3 52Cr Bose–Einstein condensate

This paper studies theoretically the spin evolution of a Bose--Einstein condensate starting from a mixture of two or three groups of ⁵²Cr (spin-3) atoms in an optical trap. The initial state is so chosen that the condensate has total magnetization zero so that the system does not distinguish up and down. It is assumed that the system is very dilute (particle number is very small), the temperature is very low, and the frequency of the harmonic trap is large enough. In these situations, the deviation caused by the neglect of the dipole--dipole interaction and by using the single-mode approximation is reduced. A theoretical calculation beyond the mean field theory is performed and the numerical results are helpful for the evaluation of the unknown strength g0.     

Applicability of coupling strength estimation for linear chains of restricted access

The characterization of an unknown quantum system requires the Hamiltonian identification. The full access to the system, however, is usually restricted, hindering the direct retrieval of the relevant parameters, and a reliable indirect estimation is usually required. In this work, based on the reformulated form of the original algorithm of Burgarth et al.[Phys. Rev. A 79 020305(2009)], the robustness of the estimation scheme against numerous sources of errors during the actual measurement is analyzed. The scheme is numerically studied for sites with a chain structure, exploring its applicability against observational errors including the limited signal-noise ratio and the finite spectral width. The spectral distribution of the end site is shown to determine the applicability of the method, and reducing the influence from truncated spectral components is critical to realize the robust reconstruction of the coupling strengths.     

The Genealogical Tree of a Chromosome

We consider a simple neutral model to describe the genealogy of chromosomes by taking into account the effects of both recombination and coalescence. Seen as a statistical physics problem, the model looks like an inverse problem: A number of properties such as pair or three-point correlations can be computed easily, but the prediction of global properties, in particular the average number of ancestors, remains difficult. In the absence of exact solutions, these global properties can nevertheless be estimated by the usual approximations: series expansions, Monte Carlo simulations, mean-field theory. Simulations exhibit also non-self-averaging properties similar to those of mean-field spin glasses.     

Fe掺杂La0．8Sr0．2Co1-xFexO3磁性的研究

利用溶胶-凝胶法制备了一系列的La0.8Sr0.2Co1-xFexO3样品.通过研究在不同外加磁场下磁化强度和温度变化的关系发现,在较高的外场下La0.8Sr0.2Co1-xFexO3样品的磁性反转现象没有被观察到;在低场下La0.8Sr0.2Co1-xFexO3系统磁性反转现象被实现.这说明Fe的掺杂引起了La0.8Sr0.2Co1-xFexO3样品中铁磁和反铁磁之间的竞争,导致了La0.8Sr0.2Co1-xFexO3样品磁性反转;同时外加磁场的强弱影响了La0.8Sr0.2Co1-xFexO3系统磁性反转现象的发生,外加磁场增大使得在La0.8Sr0.2Co1-xFexO3样品中Co离子的自旋平行趋势更强,在铁磁和反铁磁之间的竞争中铁磁耦合占主导优势,因此在较高的外场下磁性反转现象没有被观察到.     

A New Quantum State

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La0.7Sr0.3-x□xCoO3(0≤x≤0.2)钴氧化物中锶空位诱导的自旋态转变效应

研究了锶空位对La_0.7Sr_0.3-x_xCoO₃ (0≤x≤0.2)多晶钴氧化物结构、磁性和输运性质的影响.结果表明：随着锶空位浓度x的增大,A位阳离子无序度增大,导致铁磁双交换作用减弱及反铁磁超交换作用增强,两者相互竞争,出现团簇自旋玻璃态;空位浓度超过10%后,Co—O键长迅速减小,导致晶体场劈裂能加大,大部分三价钴离子以低自旋态出现,系统基态为类超顺磁态, 关键词： 空位掺杂 钴氧化物 自旋转变