量子引力场中纳米颗粒的量子理论

首次给出纳米颗粒哈密顿量的明确表示。根据纳米颗粒的量子自旋特性,得到纳米颗粒质量随时间变化的规律。根据纳米颗粒哈密顿量的守恒条件,得到纳米颗粒的量子平动动量、纳米颗粒的量子转动动量、纳米颗粒所受的量子引力及纳米颗粒与纳米颗粒引力中心的量子距离随时间变化的规律。证明纳米颗粒的量子平动动量、纳米颗粒与纳米颗粒引力中心的量子距离、纳米颗粒的量子能量均与颗粒所处的量子状态有关。对于不同量子状态的纳米颗粒,上述物理量的取值不同。本文中创新一组满足对易关系互为共轭的复量子数算符,建立纳米颗粒的量子算符代数理论,得到纳米颗粒能量的量子化表示。     

一维单原子纳米颗粒的晶格振动量子化

只考虑最近邻原子间的简谐力互作用 ,应用Dyson方程推导了一维单原子纳米颗粒的位移 -位移格林函数 ,在此基础上研究了声子结构 ,并对晶格振动进行了量子化     

超微粒子的一维振动的量子化处理

提出超微粒子的量子化处理 ,给出振动系统的湮灭算符和产生算符的新量子变换及创新的SU( 1,1)Lie代数理论 ,得到超微粒子的一维量子振动系统的完整量子理论     

重新认识重费米子超导

正在重费米子超导体中,正常态重电子的有效质量可以达到自由电子质量的上百倍,其特征费米能量也相应削减,只有meV的量级。1979年,德国科学家Frank Steglich等首先在中发现了重费米子超导,其超导转变温度约为0.6K,为重电子费米能的5%,远大于一般的元素超导体,堪称"高温超导体"。超导的发现不仅仅具有开创的意义,还确立了以磁性量子临界涨落为配对胶水,诱导重电子发生d波配对的基本理论图像,成为描述重费米子超导的标准范     

一维单原子纳米颗粒晶格振动性质的理论研究

根据一维单原子纳米颗粒晶格振动量子化的结论 ,推导了一维单原子纳米颗粒晶格振动的内能、比热、原子均方位移和原子均方速度公式 ,并进行了数值计算。数值计算结果表明 ,单位质量的一维单原子纳米颗粒的晶格振动内能与比热随纳米颗粒尺寸的增加而增加 ,一维单原子纳米颗粒的表面原子的均方位移大于内部原子的均方位移 ,而表面原子的均方速度小于内部原子的均方速度     

微观粒子量子谐振动的量子力学表征

对微观粒子量子谐振动的量子尺寸效应进行表征,给出量子谐振子精确的量子哈密顿量,建立适合量子谐振子特性的量子算符代数理论。根据创新的量子谐振子的量子算符代数理论,得到量子谐振子的能量关系。结果表明:量子谐振子的能量为常量,其值与时间量子数无关,不同时间量子态量子谐振子的能量都相同。     

纳米复合热电材料研究进展

低维化和纳米化实现电、声输运特性的协同调控从而优化热电性能是当前热电材料领域的一个重要研究方向.通过外混、原位复合等方式引入的纳米颗粒能散射具有中长波波长的声子从而降低材料的晶格热导率,同时纳米化有助于载流子在费米能级附近态密度的提高,纳米颗粒构成的界面所产生的界面势垒能有效过滤低能量载流子,从而增大赛贝克系数.纳米颗粒的含量、分散状态以及颗粒本征性质是设计高性能纳米复合热电材料的关键.对于不同材料体系,外部混合、原位氧化、分相析出等制备方法为实现微结构控制提供了可能.本文以几个典型材料体系为例介绍微结构调控提高材料热电性能的研究进展,并讨论微结构调控对电、声输运的影响机制.     

金属光电效应的量子理论

为研究金属光电效应的量子理论,给出金属中一个电子的总哈密顿量,建立适合电子量子振动特性的算符代数理论,根据量子算符代数理论,得到金属中一个电子的总能量,由光电效应理论得到一个自由光子的静止质量和一个自由光子的能量表示。     

氢原子的量子谐振动理论

给出做量子谐振动的氢原子精确的量子哈密顿量,建立适合氢原子特性的量子算符代数理论,根据创新的氢原子的量子算符代数理论,得到氢原子的能量及氢原子的光谱常数表示。结果表明:氢原子的光谱常数与实验测定值完全符合。     

类三角晶格固/固型声子晶体的带隙特性研究

首先划分7种类三角晶格声子晶体按三角点阵排列,然后利用平面波展开法计算了类三角晶格钢/环氧声子晶体的反平面模态能带结构,讨论了带隙各向同性和归一化半径对低频带隙的影响。结果表明,类三角晶格钢/环氧声子晶体可以打开不同频率段较宽带隙;选取归一化半径分别为0.34和0.38,使低频带隙得到最大值。这些带隙特征为设计新型减振材料提供了理论依据。     

A New Approach to Transport Theory of High Tc Bismuth-Based Ceramic Superconductors

A new transport theory for high temperature superconductors is propos#ed and supported with extensive calculations.The Cooper-pairs while remaining on a pseudo Fermi surface behave like weak Fermions. When the Cooper-pairs become free they behave as spinless bosons. The polarons and bipolarons are highly localized quantum states with virtually no gap existing in between them and are considered as bosons with nondegenerate spining. The binding energies of Cooper-pairs both in a weak Fermion system and for a spinless boson are calculated.A kind of a semimetallic softening transition is responsible for high temperature superconductivity and is temperature independent. There is no electron–phonon coupling for high temperature superconductors. High temperature ceramic superconductors before the onset of superconductivity are found to be Mott–Hubbard dielectric insulating materials.     

材料热力学性质的第一原理晶格振动计算研究

对计算固体物质晶格振动、研究材料的热力学性质的方法做了简要的探讨。以氧化锆为例．介绍了第一原理线性响应理论计算声子谱和声子态密度的方法．推导出热容、自由能、德拜温度等相关的热力学性质随温度的变化．并计算了氧化锆相变温度。结果表明通过这种方法无需任何实验数据完全从原子、电子层次出发进行材料热力学设计．为设计和研究全新材料体系提供了一个新的途径。     

Structural and lattice dynamical properties of Zintl NaIn and NaTl compounds

The first-principles calculations based on the density-functional theory have been performed using both the generalized–gradient approximation (GGA) and the local-density approximation (LDA) to investigate many physical properties of NaIn and NaTl compounds. Specifically, the structural (lattice constant, bulk modulus, pressure derivative of bulk modulus, phase transition pressure (P_t)), mechanical (second-order elastic constants (C_ij), Young’s modulus, isotropic shear modulus, Zener anisotropy factor, Poisson’s ratio, sound velocities), thermo dynamical (cohesive energy, formation enthalpy, Debye temperature), and the vibrational properties (phonon dispersion curves and one-phonon density of states) are calculated and compared with the available experimental and other theoretical data. Also, we have presented the temperature variations of various thermo dynamical properties such as free energy, internal energy, entropy and heat capacity for the same compounds.     

Structural,elastic, and lattice dynamical properties of YB2 compound

In this work, density functional theory calculations on the structural, mechanical, lattice dynamical, and thermodynamical properties of YB₂ in AlB₂-type and monoclinic (C2/m) structures are reported. The local density approximation has been used for modeling exchange–correlation effects. We have predicted the lattice constants, bulk modulus, elastic constants, shear modulus, Young’s modulus, Poison’s ratio, Debye temperature, and sound velocities. Furthermore, the phonon dispersion curves, corresponding phonon density of states, some thermodynamical quantities such as internal energy, entropy, heat capacity, and their temperature-dependent behaviors are presented. Our structural and some other results are in agreement with the available experimental and theoretical data.     

Quasiparticles and Polaronic Effects in Crystals,Fermi Gasses and Fermi Liquids

We study the effect of quantum and classical phase fluctuations on the phase transitions in the system of Josephson-junction arrays. We employed a variational method for calculating the Gaussian type fluctuation of the phase in the Josephson-junction array lattice systems without and with an external magnetic field. We investigate the spectrum of collective excitations and the effects of collective excitations on the transport properties of Josephson-junction arrays. We showed that the Hamiltonian for the lattice system of the Josephson junction is the same as the Hamiltonian for the classical or quantum two-dimensional interacting rotators. We also showed that the dynamics of fluctuations of the phase in the lattice system of Josephson junction is very similar to the lattice dynamics of the lattice in crystals. We also showed that in the lattice system of Josephson junctions there is the collective acoustic mode similar to the acoustic mode in the crystal lattice, and this mode may lead to the dissipation of the Josephson current in the superconducting array of Josephson junctions. The speed of sound of the collective acoustic mode of the phase fluctuation depends on the Josephson coupling energy and the Coulomb charging energy. The contribution of the collective acoustic mode to the low temperature specific heat is the same as the contribution of the acoustic phonons to the specific heat of crystals. We also discuss the future development of results and their application.     

Electron scattering and the lattice thermal conductivity of superconducting transition metal alloys

The mechanism of heat energy transport by phonon carriers which are primarily scattered by conduction electrons is re-examined for concentrated alloys in the normal and superconducting phases. The large increase in the normal state lattice thermal conductivity observed experimentally for concentrated niobium alloys, compared with the pure metal, is explained qualitatively as due to the diminished importance of scattering by d-electrons, compared with s-electrons, when the mean free path for the former becomes less than the typical phonon wavelength. Evidence is presented for the existence of a gap-less type of superconductivity in the concentrated alloys for both s and d-electrons.     

Phase Transitions and Phase Fluctuations in the Josephson-Junction Arrays

We study the effect of quantum and classical phase fluctuations on the phase transitions in the system of Josephson-junction arrays. We employed a variational method for calculating the Gaussian type fluctuation of the phase in the Josephson-junction array lattice systems without and with an external magnetic field. We investigate the spectrum of collective excitations and the effects of collective excitations on the transport properties of Josephson-junction arrays. We showed that the Hamiltonian for the lattice system of the Josephson junction is the same as the Hamiltonian for the classical or quantum two-dimensional interacting rotators. We also showed that the dynamics of fluctuations of the phase in the lattice system of Josephson junction is very similar to the lattice dynamics of the lattice in crystals. We also showed that in the lattice system of Josephson junctions there is the collective acoustic mode similar to the acoustic mode in the crystal lattice, and this mode may lead to the dissipation of the Josephson current in the superconducting array of Josephson junctions. The speed of sound of the collective acoustic mode of the phase fluctuation depends on the Josephson coupling energy and the Coulomb charging energy. The contribution of the collective acoustic mode to the low temperature specific heat is the same as the contribution of the acoustic phonons to the specific heat of crystals. We also discuss the future development of results and their application.     

Ca2YO(BO3)3晶体的热物理性质研究

测量了新型非线性激光晶体Ca2YO(BO3)3（YCOB）的比热及其沿a,b,c三个方向的热膨胀系数，热扩散系数，导热系数，声子平均自由程和等效声速等热物理性质；讨论了属于单斜晶系的YCOB晶体的热物性的各向异性行为；实验结果表明YCOB晶体具有较大的比热和导热系数，其热膨胀系数各向异性相对较小，具有良好的热物理和力学性能。     

Multiband Calculations on the Magnetic Properties of Superconductor KFe2As2

Based on two-band Ginzburg–Landau theory, we study the temperature dependence of upper critical fields for superconducting crystal KFe₂As₂. The results reproduce the experimental data in a broad temperature range and directly underlie the multigap superconductivity in this crystal. Our calculations also indicate that the specific heat jump at the superconducting critical temperature is about 0.77, in accordance with the experimental data.