Transmission spectra through photonic double quantum well system

By means of the modal expansion method with an R-matrix propagation algorithm, effects of the coupling between resonance photonic states on the resonance tunneling through a double quantum well structure are investigated. We examine the effects on the transmission spectra due to variation of the second well width and middle barrier thickness. Drastic change of the tunneling spectra is found and analyzed when the wells are filled with left-hand media.     

Transport of Spin-Polarized Current Through a Mesoscopic Ring with Two Leads Induced by Aharonov-Bohm and Aharonov-Casher Phases

We study the transport of spin-polarized current induced by the Aharonov-Bohm and Aharonov-Casher phases in a mesoscopic ring with two leads in the presence of a cylindrically symmetric electric field and the magnetic flux at the centre of the same ring. An exact solution for the quantum transport is obtained. It is shown that the transport spin-polarized current and its polarizability can be controlled by the electric field and the magnetic flux as well.     

单模光腔中N个二能级原子系统的有限温度特性和相变

本文研究单模光场中N个二能级原子Dicke模型的有限温度特性和相变. 把原子赝自旋转换为双模费米算符, 用虚时路径积分方法推导出系统的配分函数, 对作用量变分求极值得到系统的热力学平衡方程, 及原子布居数期待值和平均光子数随原子-光场耦合强度变化的解析表达式. 重点研究了在量子涨落起主导作用的低温区, 由耦合强度变化产生的从正常相到超辐射相的相变, 指出该相变遵从Landau连续相变理论, 平均光子数可作为序参数, 零值表示正常相, 大于零则为超辐射相. 在零温极限下本文的结果和量子相变理论完全符合. 另外, 本文也讨论了系统的热力学性质, 比较有限温度相变和量子相变的异同. 发现, 在强耦合区低温稳定态的光子数和平均能量都和绝对零度的值趋于一致, 而超辐射相的熵则随耦合强度的增强迅速衰减为零.     

反铁磁粒子的势助量子隧穿和宏观量子效应

用周期瞬子方法研究了反铁磁粒子中激发态量子隧道效应.给出了各种低激发态下的隧穿幅、能级分裂以及前置因子.用统计平均得到给定温度下的隧穿率.理论计算的隧穿率随温度的变化关系与实验结果相符. 关键词：     

Quantum transport through two series Aharonov--Bohm interferometers with zero total magnetic flux

With the help of nonequilibrium Green's function technique, the electronic transport through series Aharonov--Bohm (AB) interferometers is investigated. We obtain the AB interference pattern of the transition probability characterized by the algebraic sum \phi and the difference \theta of two magnetic fluxes, and particularly a general rule of AB oscillation period depending on the ratio of integer quantum numbers of the fluxes. A parity effect is observed, showing the asymmetric AB oscillations with respect to the even and odd quantum numbers of the total flux in antiparallel AB interferometers. It is also shown that the AB flux can shift the Fano resonance peaks of the transmission spectrum.     

量子玻色流体中的压缩玻色子对数态

导出参量相关的Bogoliubov幺正变换的封闭性表达式，在原粒子数表象中对角化量子玻色流体的约化Hamiltonian．将两模辐射场的非经典特性的表述推广到与流体的相互作用机制相应的量子玻色场，从波动和粒子统计的角度确认Hamiltonian本征态是非经典的压缩玻色子对数态． 关键词：     

哈密顿算符是SU（1,1）和SU（2）算子含时线性组合量子系统的时间演变及…

研究了哈密顿算符是ＳＵ（１，１）和ＳＵ（２）算子线性组合且系数显含时间量子系统的时间演化。我们发现适当选取厄密不变量，不仅可得到统一的量子态时间演化封闭解，而且可得到时间演化幺正算符。用时间演化算符我们讨论了含时双光子压缩态和ＳＵ（１，１）相干态以及ＳＵ（２）压缩态的压缩性质。     

PATH INTEGRAL CALCULATION OF QUANTUM TUNNELING FOR CUBIC POTENTIAL AT FINITE TEMPERATURE

The periodic instanton method is used to study the decay rates of metastable ground state and excited states of the cubic potential. The imaginary part of the energy is calculated through the standard procedure in the path-integral scheme. A formula of the decay rate valid for the entire region of energy is obtained. This formula provides a linkage between classical thermal activation at high temperatures and purely quantum tunneling at zero temperature. It is shown that in the low energy limit this more general result reduces exactly to the vacuum result. The temperature dependence of the decay rate agrees with earlier works in the literature.     

High-average-power, 1-MW peak-power self-mode-locked Ti:sapphire oscillator

We describe a novel self-mode-locked Ti:sapphire ring laser that produces 13-fs pulses with peak powers exceeding 1 MW, pulse energies of 13 nJ, and average mode-locked output powers of 1.5 W at a cavity repetition frequency of 110 MHz. A complete resonator analysis describing the optimum mode-locking configuration is presented, together with fringe-resolved autocorrelation and sonogram measurements of the output pulses.     

Condensate fraction of asymmetric three-component Fermi gas

In this paper, we investigate the condensate fraction （CF） of fermionic pairs in the BCS-BEC crossover for three- component Fermi gas with both asymmetric interactions and unequal chemical potentials in two-dimensional free space. By using the functional-path-integral method, we have analytically derived the number densities and bound-state energy, from which the off-diagonal long-range order is analyzed in terms of the asymptotic behavior of the two-body density matrix. The explicit formula of CF is obtained as a function of the bound-state energy and population imbalance. It is demonstrated that the CF spectrum with respect to the bound-state energy can be used to characterize the quantum phase transition between the two kinds of Sarma phases as well as the transition from three-component to two-component superfluid. Moreover we obtain the same analytic formula of CF in the BCS superfluid phase as that of homogeneous Fermi gas with equal chemical potentials.