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We investigate the distribution of the entanglement of the one-dimensional single-hole Hubbard model (HM) and study the relationship between the entanglement and quantum phase transition in the model. The von Neumann entropy of a block with neighbouring spins L for a single-hole HM is calculated using the densitymatrix renormalization group. The distributions of the entanglement entropy in the ground state, as a function of block length, show a dramatic effect, i.e. effectively decoupling with the centres, no matter how the Coulomb interaction u 〉0 or u 〈0. Contrarily, for the Coulomb interaction u = 0 or close to zero, the entanglement entropy in the single-hole model reaches a saturation value for a certain block size. For a fixed size L = 40, the ground state entanglement entropy measure, as a function of u1 shows a peak corresponding to the critical quantum phase transition. 相似文献
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Atomic simulations using embedded atom method (EAM) are performed for Cu (100) nanobelts to study the structural and mechanical behaviour. Cu (100) nanobelts are along[001] taken as the z-axis and have a rectangular cross section in the x - y plane, with [100] and [010] taken as x and y axes. The periodic boundary is used along the z-axis to simulate an infinitely long nanobelt, and other surfaces are free. The simulations are carried out under the mechanical loading with an elongation strain rate of 8.0×10^8 s^-1 along the z-axis. The results show that the nanobelt undergoes a transition from the initial structure with a (100) axis and {100} lateral surfaces to a new structure with the (112) as the z-axis and the lateral surfaces are {111} and {110} respectively, instead of the original {100} surfaces. The mechanism of the structural transition is ascribed to the dislocation propagation through the nanobelt under the external stresses. 相似文献
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A hydrated tetra-carboxylato-bridged dinuclear copper(Ⅱ) complex [Cu2(mEP)2(H2O)2]2 (1) (mEp is mono -ethyl phthalate or 1,2-benzenedicarboxylate monoethyl ester) has been prepared and characterized by X-ray diffraction single crystal structure analysis and magnetic measurements. This dinuclear complex adopts dimeric paddle-wheel cage structure and the coordination model around each copper(Ⅱ) atom is square-pyramidal with four oxygen atoms of the carboxylate groups from four different mono-ethyl phthalate ligands and one oxygen atom of water as apical position. The magnetic data for 1 exhibited strong intramolecular antiferromagnetic interaction between the two paramagnetic metal ions with 2J=-315.18 cm-1. Comparing with other related complexes in structure and magnetic propertity, the main factor which determines the strong antiferromagnetic interaction in the dimeric copper(Ⅱ) carboxylates is the electronic structure of the bridging O-C-O moiety. CCDC: 624561. 相似文献
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STUDIES ON THE NEXT-NEAREST NEIGHBOR HOPPING INTERACTIONS OF π-ELECTRONS IN QUASI-ONE-DIMENSIONAL ORGANIC FERROMAGNETIC MODEL 下载免费PDF全文
Based on a theoretical model proposed for quasi-one-dimensional organic polymer fer-romagnets, the next-nearest neighbor hopping interactions of sr-electrons are considered. Allowing for full lattice relaxation, a set of self-consistent equations is established to study the system. The spin-density-wave (SDW) and the possible ferromagnetic ground state of the system are investigated in detail. It is found that the next-nearest neighbor hopping in-teractions will make the SDW stronger and consequently make the ferromagnetic state more stable as compared with the nonmagnetic reference state. 相似文献
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一、引言自1980年至1984年,我们两人作为访问学者和研究人员(Research Associate),在美国明尼苏达大学物理系,分别进修、工作两年多时间。明尼苏达大学是美国前二十个名牌大学之一。全校有5万多名学生,18个学院,250个专业。有来自105个国家的留学生,全校有4000多名教授,其中不少是世界上有名望的学者。仅工学院380名教授中,就有7名科学院院士,13名工程科学院院士。在这段时间内,我们除参加各自的研究课题 相似文献
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本文简述了准分子激光的发展历史、原理、现状及展望,介绍了准分子激光在染料激光、光谱学、光刻、薄膜沉积、表面处理、精密机械加工及医学领域的几种主要应用. 相似文献