类Quesne环状球谐振子势场中的赝自旋对称性

提出了一种新的类Quesne环状球谐振子势,应用二分量方法求解1/2-自旋粒子满足的Dirac方程, Dirac哈密顿量由标量和矢量类Quesne环状球谐振子势构成.在Σ=S(r)+V(r)=0的条件下,得到了Dirac旋量波函数下分量的束缚态解和能谱方程, 显示出类Quesne环状球谐振子势场中的赝自旋对称性.讨论了束缚态波函数和能谱方程的有关性质. 关键词： 类Quesne环状球谐振子势 Dirac方程 赝自旋对称性 束缚态     

一维压电Fibonacci类准周期声子晶体传输特性

基于传输矩阵法研究了一维压电Fibonacci类准周期声子晶体的传输特性, 比较了一维Fibonacci序列压电准周期声子晶体与非压电准周期声子晶体以及压电周期性声子晶体的透射性. 计算结果表明:弹性波通过一维准周期结构压电声子晶体时与周期性声子晶体一样会有带隙的出现, 且发现具有压电性的Fibonacci序列准周期声子晶体禁带宽度发生了展宽. 进一步讨论了入射角度对固定频率下声子透射系数的影响,结果表明一维压电Fibonacci序列准周期结构声子透射性依赖于入射角度的选取.     

准周期外力驱动下Lorenz系统的动力学行为

本文研究了准周期外力驱动下Lorenz系统的动力学行为，发现当外强迫的振幅达到某一个临界值时，系统的动力学行为将会发生根本性的变化，由此揭示了产生非混沌奇怪吸引子(Strange Nonchaotic Attractor, SNA)的一个新机制：准周期外强迫振幅的加大导致系统由奇怪的混沌吸引子转变为SNA，系统的相空间最终被压缩至一个准周期环上.并且本文的结果表明，外强迫的临界振幅与Lorenz系统Rayleigh数的大小成正比，而其受外强迫频率变化的影响并不大. 关键词： 准周期 Lorenz系统 非混沌奇怪吸引子     

约瑟夫逊结中准周期通向混沌的测量

本文利用约瑟夫逊结电子模拟器测量了由二个外加交流信号源驱动的约瑟夫逊结系统从准周期通向混沌的特性,给出了当外加信号源的二个频率比值w为不同值时所对应的庞卡勒截面图和结电压的波形图;改变信号源的振幅测量了系统从准周期通向混沌的运动过程;在状态图A_1/A_(1c)～A_2/A_(2c)上,一条曲线将平面分为准周期区域和混沌区域;利用实验方法得到二个收敛常数δ和α,其值与理论计算值符合尚好。     

一维周期与准周期排列沟槽结构的流体减阻特性研究

本文设计了具有相同平均沟槽密度的三种排列类型的一维沟槽结构: 密排列、周期间隔排列和两种准周期间隔排列, 并采用数值模拟和实验验证相结合的方法研究了一维沟槽结构在不同排列下的流体减阻特性. 模拟计算分析流场特征和总阻力, 发现相对于密排列和周期间隔排列的沟槽结构, 准周期间隔排列具有更好的减阻特性, 并且这一结果得到减阻实验的验证. 通过流场分布特性进一步分析沟槽结构的减阻机理. 机理分析发现高速流在经一维准周期结构的扰动波调制后形成了准周期间隔排列的速度条纹相, 这有效地抑制了大涡在流向和展向上的形成, 从而实现较大幅度的减阻. 同时对比分析沟槽排列结构调制展向涡和流向涡各自对流动减阻的贡献, 结果表明, 调制流向涡对减阻的作用更大. 关键词： 流体减阻 沟槽结构 准周期     

少周期飞秒准径向偏振光的超快瞬变聚焦矢量场

研究了基于腔外螺旋相位调制获取高峰值功率飞秒准径向偏振光的方法,结果表明该方法所产生的并非完全纯净的径向偏振光,其径向分量决定了聚焦后纵场的分布,而径向和角向分量共同影响了横场的分布.根据Richard-Wolf矢量衍射理论模拟得到不同纯度下的少周期飞秒准径向偏振光在焦点附近的电场的时空矢量分布,发现其具有中心对称和震荡衰减特点,载波包络相位将对聚焦场的矢量时空分布产生显著影响,从而对飞秒脉冲与电子在聚焦场中的相互作用产生影响.研究结果可为进一步的激光粒子加速分析以及偏振转换器的设计提供依据.     

相对论性非球谐振子势场中的赝自旋对称性

求解了非球谐振子势场中1/2自旋粒子满足的Dirac方程,Dirac哈密顿量包含有标量非球谐振子势S(r)和矢量非球谐振子势V(r).在Σ(r)=S(r)+V(r)=0和Δ(r)=V(r)-S(r)=0的条件下,解析地得到了Dirac旋量波函数的束缚态解和能谱方程,结果表明非球谐振子势 关键词： 非球谐振子势 Dirac方程 赝自旋对称性 束缚态     

有限温度下Na_4 团簇赝转动的局域Lyapunov指数研究

:在紧束缚分子动力学模型基础上,对具有D2h对称性的Na4团簇在不同温度T=76K、112K、212K和224K下的热力学行为进行了研究。根据局域Lyapunov指数分布的变化,对由温度T=76K、112K向温度T=212K、224K的变化中会出现的赝转动所表现的混沌现象进行了分析     

一维Fibonacci准周期Frustrated Ising模型的热力学特性

分别给出周期和自由边界条件下求解一维Fibonacci准周期Frustrated Ising模型的配分函数的方法。研究它的低温热力学性质,发现当温度趋于零时,其热力学函数在参数b/J=2/(2m+1)(m为正整数)处发生尖锐的变化。分析了零温时系统在不同参数范围内的基态构形,对计算的结果进行了解释。 关键词：     

Ising model in a quasiperiodic transverse field,percolation, and contact processes in quasiperiodic environments

Quantum Ising models in a transverse field are related to continuous-time percolation processes whose oriented percolation versions are contact processes. We study such models in the presence of quasiperiodic disorder and prove localization in the ground state, no percolation, and extinction, respectively, for sufficiently large disorder.     

The Ising chain with nonconstant external field

We give an exact computation of the Ising chain with nonconstant external field in terms of certain continued fractions. We then apply our general method to a specific example.     

Ferroelectricity in a diatomic Ising chain as investigated by the elastic Ising model

An elastic Ising model for a one-dimensional diatomic spin chain is proposed to explain the ferroelectricity induced by the collinear magnetic order with a low-excited energy state. A statistical theory based on this model is developed to calculate the electrical and magnetic properties of Ca₃CoMnO₆, a typical quasi-one-dimensional diatomic spin chain system. The calculated ferroelectric polarization and dielectric susceptibility show a good agreement with recently reported data on Ca₃Co_2-xMn_xO₆ (x ≈0.96) (Phys. Rev. Lett. 100 047601 (2008)), although the predicted magnetic susceptibility does not coincide well with experiment. We also address the rationality and deficiency of this model by including a first-order correction which improves the consistency between the model and experiment.     

Ferroelectricity in diatomic Ising chain as investigated by elastic Ising model

An elastic Ising model for a one-dimensional diatomic spin chain is proposed to explain the ferroelectricity induced by the collinear magnetic order with a low-excited energy state. A statistical theory based on this model is developed to calculate the electrical and magnetic properties of Ca₃CoMnO₆, a typical quasi-one-dimensional diatomic spin chain system. The calculated ferroelectric polarization and dielectric susceptibility show a good agreement with recently reported data on Ca₃Co_2-xMn_xO₆ (x ≈0.96) (Phys. Rev. Lett. 100 047601 (2008)), although the predicted magnetic susceptibility does not coincide well with experiment. We also address the rationality and deficiency of this model by including a first-order correction which improves the consistency between the model and experiment.     

Phase transitions in the Ising model with transverse field

We show the existence of a phase transition in the Ising model with transverse field for dimensionsv 2 provided the transverse term is sufficiently small. This is done by proving long-range order occurs using the reflection positivity of the Hamiltonian and localization of eigenvectors.     

Quasicrystal Ising chain and automata theory

An automatic sequence is generated by a finite machine (automaton). These sequences can be periodic or not: in the latter case however, they are not random, but rather quasicrystalline. We consider an Ising chain with variable interaction in a uniform external field, at zero temperature, and prove that, if this interaction is automatic, then the induced magnetic field is also automatic.     

Energy Spectrum of Bound-Spinons in the Quantum Ising Spin-Chain Ferromagnet

We study the excitation energy spectrum in the S=1/2 ferromagnetic Ising spin chain with the easy axis z in a magnetic field h={h _x ,0,h _z }. According to Wu and McCoy’s scenario of weak confinement, the fermionic spinon excitations (kinks), being free at h _z =0 in the ordered phase, are coupled into bosonic bound states at arbitrary small h _z >0. We calculate the energy spectrum of such excitations in the leading order in small h _z , using different perturbative methods developed for the similar problem in the Ising Field Theory.     

Thermodynamic properties of the mixed spin-1/2 and spin-1 Ising chain with both longitudinal and transverse single-ion anisotropies

The mixed spin-1/2 and spin-1 Ising chain with both longitudinal and transverse single-ion anisotropies is solved exactly by means of a mapping to the spin-1/2 Ising chains with alternating transverse fields and the Jordan-Wigner transformation. Within this scheme, the thermodynamic quantities of this model are rigorously determined by a recursion formula derived for the partition function based on the reduced spin-1/2 transverse Ising model. The corresponding thermodynamic properties are calculated and discussed.     

Enhancement of next-nearest-neighbouring entanglement in quantum Ising spin chain

Using the method of the Jordan--Wigner transformation for solving different spin--spin correlation functions, we have investigated the generation of next-nearest-neighbouring entanglement in a one-dimensional quantum Ising spin chain with the Gaussian distribution impurities of exchange couplings and external magnetic fields taken into account. The maximal value of entanglement between the next-nearest-neighbouring qubits in the transverse Ising model was analysed in detail by varying the effectively controlled parameters such as interchange coupling, magnetic field and the system impurity. For such systems, where both exchange couplings and external magnetic field disorder appear, we show that it is possible to achieve next-nearest-neighbouring entanglement better than the previously discussed pure Ising spin chain case. We also show that the Gaussian distribution impurity can induce next-nearest-neighbouring entanglement, which can be used as a means to characterize quantum phase transition.