光格子中玻色-爱因斯坦凝聚体的超流相

本文采用Bogliubov方法分析了光格子中玻色-爱因斯坦凝聚体的能谱,得到超流-Mott相变条件,指出光格子中BEC是一种典型的超流态,最后给出了超流速度.     

A Possible Explanation to Paradox in Horse Spleen Ferritins

There are contradicting opinions about the tunnelling experiments in horse-spleen ferritin particles.By distinguish the coherent and incoherent tunnelling processes,we give a unified explanation to different experiments.As a rsult,a possible explanation to the paradox is proposed.     

Electron resonance-transmission through a driven quantum well with spin--orbit coupling

We have studied the spin-dependent electron transmission through a quantum well driven by both dipole-type and homogeneous oscillating fields. The numerical evaluations show that Dresselhaus spin-orbit coupling induces the splitting of asymmetric Fano-type resonance peaks in the conductivity, in which the dipole modulation and the homogeneous modulation are equivalent. Therefore, we predict that the dipole-type oscillation, which is more practical in the experimental setup, can be used to realize the tunable spin filters by adjusting the field oscillation-frequency and the amplitude as well.     

Field-assisted electron transport through a symmetric double-well structure with spin--orbit coupling and the Fano-resonance induced spin filtering

We have investigated theoretically the field-driven electron-transport through a double-quantum-well semiconductor-heterostructure with spin-orbit coupling. The numerical results demonstrate that the transmission spectra are divided into two sets due to the bound-state level-splitting and each set contains two asymmetric resonance peaks which may be selectively suppressed by changing the difference in phase between two driving fields. When the phase difference changes from 0 to π, the dip of asymmetric resonance shifts from one side of resonance peak to the other side and the asymmetric Fano resonance degenerates into the symmetric Breit-Wigner resonance at a critical value of phase difference. Within a given range of incident electron energy, the spin polarization of transmission current is completely governed by the phase difference which may be used to realize the tunable spin filtering.     

LARMOR PRECESSION AND THE BARRIER INTERACTION TIME

The Larmor precession of a spinning particle in a magnetic field confined in the region of one dimensional-rectangular barrier is investigated with the spin coherent state of incoming particle, which has advantage to recognize the equation of the spin precession. Our new observation is that the precession time of spin is uniquely determined and is seen to be equal to the dwell time.     

可用于拓宽光波单向传输带宽的光子晶体异质结构界面

基于光波单向传输的全光二极管在集成光通信、全光网络和光信息处理中有重要应用.基于方向带隙失配设计的光子晶体异质结构可实现光波单向传输,但正向透射率较低,带宽较窄.基于对光子晶体异质界面倾斜角度的研究,根据界面全反射条件,利用可集成材料硅和二氧化硅设计了一种空气孔型二维光子晶体异质结构.异质结构界面两侧的光子晶体对1550 nm波长附近的TE模光波在Γ-X方向均呈导带,避免了方向带隙失配.研究发现当异质界面满足全反射条件时,由于光子晶体的自准直效应,较宽波段的正向光波得以高效传播,而反向光波在界面由于全反射而被禁止传播.光子晶体异质结构界面的全反射效应打破了方向带隙对光波单向传输的限制,使得反向光波在光子晶体中为导带时同样可实现近零透射率,从而拓宽了光波单向传输的波长范围.基于全反射界面的光子晶体异质结构经过优化后,其正向透射率达0.64,透射对比度为0.97,单向传输带宽可达553 nm.     

自旋相干态变换和自旋-玻色模型的基于变分法的基态解析解

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     

光子晶体双量子阱的共振隧穿

采用R矩阵法研究了二维光子晶体双量子阱的共振隧穿特性.研究发现:光子晶体双量子阱的共振频率可以通过调节双阱的耦合强度来控制;对称双量子阱中,共振峰发生双劈裂;不对称双量子阱,共振劈裂消失.但是,由改变左手介质和右手介质在双阱中的排列顺序产生的阱介质不对称阱的共振劈裂消失与阱宽不对称的双阱产生的共振劈裂消失不一样.进一步对一维光子晶体量子阱分析后发现,前者是由光在左右手介质中传播的能流方向相反产生干涉相消而引起;后者是由阱宽不同,阱的本征模不一样而引起. 关键词： 光子晶体 双量子阱 R矩阵')" href="#">R矩阵 左手介质     

Quantum Effects of Many Atoms in Spinor Bose-Einstein Condensates

We have studied the evolutions of the population transfer, tunnelling current and antibunching effects between spin-（＋1） and spin-（-1） in the case of the strong laser pulses. It is found that the population transfer and tunnelling current exhibit periodical oscillation. For the same Rabi frequency, the larger the atom number, the longer the oscillation period is. For the spin-（-1） component, when the atomic numbers are N=4 and 10, the antibunching effect can appear. For different atomic numbers, the appearing regions are very different. For spin component ＋1, the antibunching effect can always appear for different atomic numbers.     

Time evolution of atomic inversion in a standing wave light field

The interaction between an atomic beam of two-level atoms and a standing wave light field has been studied by the exact solution of a time-dependent quantum system developed recently. When the initial atomic state is choosen to be ground, we find that with the limit of zero detuning the atoms will oscillate between the upper and the lower levels with a decaying amplitude. The most interesting result obtained in this paper is when the initial atomic state is a particular superposition of the two levels, now the system does not oscillate at any time.