共查询到20条相似文献,搜索用时 171 毫秒
1.
一维分子晶体中的极化子 总被引:3,自引:3,他引:0
本文从量子化的Holstein模型出发,运用相干态展开法和能量极小原理,通过实施连续近似得到了一维分子晶体模型处于基态的极化子满足的非线性薛定谔方程及其定态孤子解、基态能量、晶格位移,其结果与Holstein T[1].从半经典理论所得的结果完全一致,因此相干态展开方法在处理与极化子有关的其他物理问题中是一种非常有效的方法. 相似文献
2.
采用LLP变分法研究了抛物量子阱中极化子的Rashba效应,得到了极化子基态能量的表达式,并讨论了半阱宽及波矢与基态能量之间的关系.结果显示,基态能量是半阱宽和电子-声子耦合强度的减函数,而是波矢的增函数.由于Rashba效应基态能量零自旋轨道分裂成两支. 相似文献
3.
提出一种基于自旋相干态变换求解自旋-玻色模型基态的变分法, 并将其用于单原子模型, 得到旋波近似和非旋波近似情形下的解析基态能量和波函数, 特别是在光场与原子的弱、强耦合区域都与数值对角化结果符合得很好. 另外, 该方法也可以直接用于求解任意原子数的Dicke模型基态和相应的量子相变研究, 而通常基于Holstein-Primakoff变换的变分法, 原则上只适用于原子数趋于无穷的热力学极限情形.
关键词:
自旋相干态
变分法
J-C模型 相似文献
4.
5.
6.
为进一步减少迭代次数和改善解的质量,对蚁群优化方法进行改进.在求解体系基态能上与传统的变分法相比有很大的优势.求解了氦原子基态能量,并应用于不同半径量子点中砷化镓类氢施主基态能量的计算.通过与变分法和遗传算法的比较,展示了算法的性能. 相似文献
7.
根据Pekar类型变分法在电子与声子强耦合的条件下计算了抛物量子点中强耦合极化子的基态能量.讨论了电子-声子耦合强度,量子点受限长度对基态能量的影响,同时引进温度参数并讨论了其对基态能量的影响,结果得出在低温的条件下,耦合强度和受限长度对基态的能量影响起主要作用;在高温的条件下,温度对基态的能量影响起主要作用,而耦合强度与受限长度的影响很小. 相似文献
8.
利用玻尔处理氢原子基态的方法,在假定了氢分子基态的半经典模型后,给出了氢分子基态能量与电子轨道半径.该结果可以与实验结果和量子变分法的计算结果相比较,对理解共价键的物理本质有一定意义. 相似文献
9.
利用能量泛函变分法研究了一维Bose-Fermi系统稳定基态的存在条件.根据Bose-Fermi系统的Lagrange量可以得到三维Bose-Fermi体系所满足的非线性动力学方程组.当外势阱的横向囚禁频率远大于轴向囚禁频率时,体系可以当作一维模型来处理.从描述三维体系的动力学方程可以得到描述一维体系的动力学方程,选取适当的无量纲参数,可以对一维动力学方程组进行无量纲处理,得到数值计算和理论分析中常用到的无量纲方程.选择高斯型试探解(简单孤立子解),利用能量泛函变分法得到一维Bose-Fermi体系稳定的
关键词:
Bose-Fermi
稳定性
基态
临界条件 相似文献
10.
利用能量泛函变分法研究了一维Bose-Fermi系统稳定基态的存在条件.根据Bose-Fermi系统的Lagrange量可以得到三维Bose-Fermi体系所满足的非线性动力学方程组.当外势阱的横向囚禁频率远大于轴向囚禁频率时,体系可以当作一维模型来处理.从描述三维体系的动力学方程可以得到描述一维体系的动力学方程,选取适当的无量纲参数,可以对一维动力学方程组进行无量纲处理,得到数值计算和理论分析中常用到的无量纲方程.选择高斯型试探解(简单孤立子解),利用能量泛函变分法得到一维Bose-Fermi体系稳定的高斯型孤立子存在条件.分析了两种特殊情况下孤立子能够稳定存在的区域以及原子数的临界条件,最后得出了一般情况下稳定基态存在时临界散射长度与原子数以及波包宽度之间的关系. 相似文献
11.
12.
13.
Few-electron systems confined in two-dimensional parabolic quantum dots at high magnetic fields are studied by the Hartree-Fock (HF) and exact diagonalization methods. A generalized multicenter Gaussian basis is proposed in the HF method. A comparison of the HF and exact results allows us to discuss the relevance of the symmetry of the charge density distribution for the accuracy of the HF method. It is shown that the energy estimates obtained with the broken-symmetry HF wave functions become exact in the infinite magnetic-field limit. In this limit the charge density of the broken-symmetry solution can be identified with the classical charge distribution.Received: 24 October 2003, Published online: 6 January 2004PACS:
73.20.Qt Electron solids - 73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems 相似文献
14.
D. Kulak 《Czechoslovak Journal of Physics》2001,51(9):889-895
In this paper a variational method for the ground state energy approximation of theE−b
1,b
2 Jahn-Teller system is presented. This method is based on the choice of a suitable variational ground state wave function.
This trial wave function — a correlated squeezed state — is used to account for the correlation and anharmonicity of the interaction
between the two vibrational modes; the anharmonicity of both modes is taken into account by the squeeze effects of these modes.
The ground state of mode 1 in this trial wave function is considered as a linear combination of the two displaced harmonic
oscillators. The ground state energies for the linearE - e Jahn-Teller system calculated by this method are not only in good agreement with the exact diagonalization results, but they
are also better than those from the previous analytical studies. Another conclusion which results from the presented model
is the following one: the squeezing effect of mode 1 for the linearE - e Jahn-Teller system is substantially smaller, in contrast with the results which are presented in the previous analytical
studies. 相似文献
15.
A microscopic investigation of giant-resonance states in open-shell nuclei is proposed using for the representation of the wave functions the shell-model basis in a large model space. Instead of an exact diagonalization of the hamiltonian, which is essentially impossible for the large model spaces considered, an iterative procedure is used, which is based on the Lanczos algorithm for matrix diagonalization. The choice for the initial state in this iteration ensures that the complete transition strength to the resonance of interest is taken into account, and the iteration allows an increasingly accurate estimate of the spreading of this transition strength to more complicate configurations. An application of this method to the giant dipole resonance in 20Ne yields stable results after a few iteration steps and demonstrates the efficiency of this method. 相似文献
16.
S. Siljamki A. Harju E. Rsnen J. Suorsa R.M. Nieminen 《Physica E: Low-dimensional Systems and Nanostructures》2005,26(1-4):441
Unsymmetrical quantum-dot systems are generally difficult to study using wave-function techniques, like quantum Monte Carlo (QMC) or exact diagonalization (ED) methods. The initial trial wave function for Monte Carlo methods is difficult to find, and the exact diagonalization method can only handle very few particles.In this article a two-dimensional semiconductor quantum dot containing a non-centered impurity ion is studied, using a new exact wave-function method. Results are analyzed and compared to density-functional-theory calculations. The computational method allows one to relax the commonly used lowest-Landau level (LLL) approximation, and it's effects are studied, e.g., on the charge and current density profiles.The method, which is a combination of QMC and ED methods, is described. It combines the scalability of Monte Carlo methods with the benefits of exact diagonalization, and allows one to accurately obtain the wave function for unsymmetrical quantum dots up to more than ten electrons. Also, excited states are accessible and are analyzed in this article. 相似文献
17.
W.H. Wong C.F. Lo 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(2):213-223
In the present work we have developed an optimal coupled-cluster approximation, which can take care of both the accuracies
of the ground-state energy and the wavefunction estimates, for the ground state of a two-state system coupled to a dispersionless
boson bath. This new approach is also able to give a tight upper bound to the ground-state energy of the system. Up to the
fourth level of this approximation our results show excellent agreement with the numerical exact diagonalization results.
In particular, our results suggest no discontinuous localization-delocalization transition of the two-state system. This is
consistent with the exact result.
Received: 11 March 1998 / Accepted: 23 June 1998 相似文献
18.
We consider a simple collinear collision of a “classical“ particle with a harmonic oscillator within quantumsemiclassical model and full quantum dynamics model,in which the latter is solved analytically in squeezed state and exact diagonalization methods and acts as the exact solution of such a system.A comparison of these two models for different mass ratios between the “classical“ particle and the quantum particle is done,which gives a criterion when using the quantum-semiclassical model. 相似文献
19.
A complete phase diagram of the uniaxial brickwork lattice is determined first by using exact results, and then by using the cluster variation method. Both results are in very good agreement, which demonstrates the reliability of the CVM for two-dimensional systems. A well-defined maximum in the exact specific heat and a divergence of the CVM susceptibility provide strong indication for the occurrence of a floating phase. 相似文献
20.
Validation of the Ability of Full Configuration Interaction Quantum Monte Carlo for Studying the 2D Hubbard Model
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
《中国物理快报》2017,(8)
To validate the ability of full configuration interaction quantum Monte Carlo(FCIQMC) for studying the 2 D Hubbard model near half-filling regime, the ground state energies of a 4 x 4 square lattice system with various interaction strengths are calculated. It is found that the calculated results are in good agreement with those obtained by exact diagonalization(i.e., the exact values for a given basis set) when the population of psi particles(psips) is higher than the critical population required to correctly sample the ground state wave function. In addition, the variations of the average computational time per 20 Monte Carlo cycles with the coupling strength and the number of processors are also analyzed. The calculated results show that the computational efficiency of an FCIQMC calculation is mainly affected by the total population of psips and the communication between processors. These results can provide useful references for understanding the FCIQMC algorithm, studying the ground state properties of the 2 D Hubbard model for the larger system size by the FCIQMC method and using a computational budget as effectively as possible. 相似文献