Binding energy and photoionization cross-section of a hydrogen-like donor impurity in a quantum well-wire in a magnetic field

The effect of a uniform longitudinal magnetic field on the binding energy and photoionization cross-section of a hydrogen-like donor impurity is studied for a semiconductor quantum well-wire approximated by a cylindrical well of finite depth. The selection rules and analytical expressions for the photoionization cross-section are obtained depending on the magnetic field induction, impurity position, and light wave polarization.     

Ternary eutectic growth of Ag-Cu-Sb alloy within ultrasonic field

The liquid to solid transformation of ternary Ag42.4Cu21.6Sb36 eutectic alloy was accomplished in an ultrasonic field with a frequency of 35 kHz, and the growth mechanism of this ternary eutectic was examined. Theoretical calculations predict that the sound intensity in the liquid phase at the solidification interface increases gradually as the interface moves up from the sample bottom to its top. The growth mode of (ε θ Sb) ternary eutectic exhibits a transition of "divorced eutectic- mixture of anomalous and regular structures-regular eutectic" along the sample axis due to the inhomogeneity of sound field distribution. In the top zone with the highest sound intensity, the cavitation effect promotes the three eutectic phases to nucleate independently, while the acoustic streaming efficiently suppresses the coupled growth of eutectic phases. In the meantime, the ultrasonic field accelerates the solute transportation at the solid-liquid interface, which reduces the solute solubility of eutectic phases.     

Boltzmann distribution of free energies in a finite-connectivity spin-glass system and the cavity approach

At sufficiently low temperatures, the configurational phase space of a large spin-glass system breaks into many separated domains, each of which is referred to as a macroscopic state. The system is able to visit all spin configurations of the same macroscopic state, while it can not spontaneously jump between two different macroscopic states. Ergodicity of the whole configurational phase space of the system, however, can be recovered if a temperature-annealing process is repeated an infinite number of times. In a heating-annealing cycle, the environmental temperature is first elevated to a high level and then decreased extremely slowly until a final low temperature T is reached. Different macroscopic states may be reached in different rounds of the annealing experiment; while the probability of finding the system in macroscopic state α decreases exponentially with the free energy F _α (T) of this state. For finite-connectivity spin glass systems, we use this free energy Boltzmann distribution to formulate the cavity approach of Mézard and Parisi [Eur. Phys. J. B, 2001, 20: 217] in a slightly different form. For the ±J spin-glass model on a random regular graph of degree K = 6, the predictions of the present work agree with earlier simulational and theoretical results.      

大学物理实验的简化与深化

以复摆实验、地磁实验和衍射光栅实验为例,说明在大学物理实验中,通过提供简单的实验器材,就可以将实验内容延伸扩展,将原来内容单一的实验扩展为多层次、多目的的实验项目,实现大学物理实验的简化与深化.     

高温超导体环流演示仪

利用永磁铁对超导样品进行激励,产生的超导环流不衰减,由此原理制做了高温超导环流演示仪,该仪器可演示零电阻现象、环流磁场及超导体电阻与温度的关系.     

利用迈克耳孙干涉仪重建蜡烛火焰温度场

利用教学实验中的迈克耳孙干涉仪,进行蜡烛火焰温度场的测量.对干涉条纹进行了处理和细化,并分别用阿贝尔变换法和环带法对蜡烛火焰的温度场进行了计算,得到蜡烛火焰横截面上温度场的定量结果.     

磁场中夸克物质的黏滞系数

研究了磁场中夸克非轻子弱作用过程的反应率和黏滞系数. 改进了在弱磁场情况下的近似计算方法, 给出了非轻子过程的反应率与夸克物质的体黏滞系数的表达式, 显示出在弱磁场情况下, 黏滞系数的温度依赖关系与零磁场情况下一致, 但黏滞系数的大小依赖磁场的强度.     

强外加电场与大调制度下光折变动力学光栅形成研究

强外加电场与大调制度在光折变效应的研究中已经得到了广泛应用。采用PDECOL算法,严格求解光折变带输运方程,得到外加电场时不同调制度下光折变晶体中随时间变化的空间电荷场、载流子浓度,并讨论了外加电场对它们的影响。通过将物质方程与耦合波方程联立数值求解,可得到光折变光栅形成过程中两波耦合增益系数以及光束条纹相位的变化。模拟结果表明,在强外加电场作用下,两束记录光之间的光强与相位耦合都得到了增强,而原有的解析式忽视了强外加电场与大调制度对空间电荷场相位耦合的影响,此时不再适用。同时发现折射率光栅与记录光束条纹均发生弯曲,并不再保持平行。     

高斯光束在外加空间调制电场的光折变晶体中的演化

研究了高斯光束在外加空间调制电场的光折变晶体中的演化,结果表明,在不同的外加调制电场作用下高斯光束的光场分布会随着外电场变化而被调制。重点研究了同相位和反相位以及相位差为π/2的高斯光束在外加空间调制电场的光折变晶体中的相互作用,在外加空间分布线性增加电场作用下出现了许多新的实用特性,通过调整外加电场分布,可以让两同相位相干光靠得更近而不发生融合,也可以让两靠得很近的反相位光束可控偏转,还可以控制相位差为π/2的两相干光束进行能量转移。这种连续变化的电场可以用阶梯分布的电场替代,为工程实现提供了可能。