第12届全国凝聚态理论和统计物理学术会议简讯

受中国物理学会凝聚态理论与统计物理专业委员会的委托 ,由上海交通大学物理系承办的第 12届全国凝聚态理论和统计物理学术会议于 2 0 0 3年 10月 15日至 19日在上海举行 .参加本次会议的有来自全国各地 (包括香港地区 )高等学校和研究单位的正式代表 2 10名 ,大多数是中青年物     

石墨烯纳米片磁有序和自旋逻辑器件第一原理研究

尺寸效应和拓扑阻挫能够在有限石墨烯纳米片段中形成磁有序,本文对能够产生大自旋或电子自旋反铁磁耦合的石墨烯有限片段进行合理分类,提出几种能够作为基本逻辑门的特殊结构并对其进行第一原理电子结构计算,为设计高密度超快自旋器件提供了有效方案和理论依据.计算结果证明：基于有限石墨烯片段的逻辑门结构能够在室温下进行错误率较低的可纠错运算.     

The spin-one Duffin Kemmer Petiau equation in the presence of pseudo-harmonic oscillatory ring-shaped potential

The Duffin-Kemmer-Petiau equation （DKP） is studied in the presence of a pseudo-harmonic oscillatory ring-shaped potential in （1 ＋ 3）-dimensional space-time for spin-one particles. The exact energy eigenvalues and the eigenfunctions are obtained using the Nikiforov-Uvarov method.     

Representation of Spin Group Spin（p, q）

The representation η（P, q） of spin group Spin（p, q） in any dimensional space is given by induction, and the relation between two representations, which are obtained in two kinds of inductions from Spin（p, q） to Spin（p ＋ 1, q ＋ 1） are studied.     

稀磁半导体的制备与性质

报道了稀磁半导体的制备、性质与实验研究进展，介绍了稀磁半导体的应用及发展前景．     

铝原子正离子团簇Al+5稳定结构的理论研究

采用密度泛函理论的4种方法杂化密度泛函B3LYP与B3PW91, Perdew-Wang91交换与关联泛函WP91PW91、局域自旋密度近似SVWN, 研究了铝原子正离子团簇Al+5的多种可能结构, 找到了一种新的最稳定的结构与自旋态, 即单重态三维C2v结构, 并对上述4种DFT方法在结构优化与频率计算方面作了比较与讨论.     

Mott physics, sign structure, ground state wavefunction, and high-T c superconductivity

In this article I give a pedagogical illustration of why the essential problem of high-T _c superconductivity in the cuprates is about how an antiferromagnetically ordered state can be turned into a short-range state by doping. I will start with half-filling where the antiferromagnetic ground state is accurately described by the Liang-Doucot-Anderson (LDA) wavefunction. Here the effect of the Fermi statistics becomes completely irrelevant due to the no double occupancy constraint. Upon doping, the statistical signs reemerge, albeit much reduced as compared to the original Fermi statistical signs. By precisely incorporating this altered statistical sign structure at finite doping, the LDA ground state can be recast into a short-range antiferromagnetic state. Superconducting phase coherence arises after the spin correlations become short-ranged, and the superconducting phase transition is controlled by spin excitations. I will stress that the pseudogap phenomenon naturally emerges as a crossover between the antiferromagnetic and superconducting phases. As a characteristic of non Fermi liquid, the mutual statistical interaction between the spin and charge degrees of freedom will reach a maximum in a high-temperature ??strange metal phase?? of the doped Mott insulator.     

Frequency locking,quasiperiodicity,and chaos in dual-frequency loss-modulated erbium-doped fiber lasers

Dynamic behaviors of the erbium-doped fiber laser （EDFL） with dual-frequency loss modulation are experimentally investigated. Frequency-locked states with their winding numbers which form the devil＇s staircase are observed in this kind of lasers. In the unlocked regions, the output state changes from quasiperiodicity to chaos under increasing modulation index, which demonstrates a different route to chaos from the conventional loss-modulated EDFLs with a single modulation frequency. The chaos output in the dual-frequency loss-modulated EDFLs shows less harmonic components of the modulation frequency in the corresponding power spectrum, indicating the improvement of the randomness of the chaotic signals.     

磁场对异质界面上D-中心的影响

势阱中的类氢杂质的能级问题一直为学术界所长期关注。讨论了异质界面上中性施主D⁰和负施主离子D^-的能量随垂直于界面的磁场的变化情况,同时将磁场和势阱结合起来考虑其对类氢杂质的影响。研究发现随磁场的增大,其对D⁰基态能的影响越来越大,对其束缚能的影响逐渐变小,而对D^-中心,磁场的作用使得D^-由非束缚态转变为束缚态。计算中分别选取了两种不同的波函数,分析了这两种波函数的适用范围,利用变分的方法得到此结构中D⁰中心的基态能量和束缚能与D^-中心角动量L=-1自旋三重态的本征能量和束缚能随磁场的变化关系,找到了此三重态由非束缚态转变到束缚态对应磁场的阈值。     

On the Ground State of Spin Systems with Orbital Degeneracy

In order to understand the properties of the spin system with orbital degeneracy,we first study the ground state of the SU(4) spin-orbital model on a square lattice.The mean-field results suggest that for a small Hund‘s interaction,the flavor liquid state is stable against the solid state,but with sufficient deviation from the SU(4) limit the long-range order may be attained in 2D system.Furthermore,we employ a variational approach to calculate the phase diagram of the ground state and the temperature-dependent susceptibility by taking into account the Hund‘s interaction and the anisotropy in orbital wavefunctions.Finally,the implications for the experimental observations on the material,LiNiO2,are discussed.