Effective interaction of electrons in quantum wells

Effects of electron-phonon interaction on the interaction between electrons in semiconductor quantum wells are considered. It is found that the direct Coulomb potential between electrons in a quantum well is smaller than that in bulk semicondutors. The antisymmetric modes of the confined bulk phonons and interface phonons have no contribution to the effective interaction of electrons. If a well is narrow enough, the effective interaction between electrons caused by interaction with interface phonons may exceed that by interaction with confined bulk phonons. In narrower wells the effective interaction potential of electrons produced by phonons is stronger, but decreases rapidly with increasing distance between electrons.     

The Dzyaloshinskii-Moriya interaction in metals

The Dzyaloshinskii-Moriya (DM) interaction in metals is an important mechanism for many magnetic properties. We start with the s-d exchange model and spin-orbit interaction for weak itinerant ferromagnetic systems to establish the form of DM interaction for metallic magnetic systems. The s-d exchange interaction is treated accurately and the conduction electron-mediated magnetism gives a form of DM interaction which is different from that in insulators. The implications of our result to spiral spin states and skyrmion lattices are also discussed.     

A Separable Pairing Force in Nuclear Matter

The method introduced by Duguet is adopted to derive a separable form of the pairing interaction in the ^1So channel from a bare or an effective nucleon-nucleon （NN） interaction in nuclear matter. With this approach the separable pairing interaction reproduces the pairing properties provided by its corresponding NN interaction. In this work, separable forms of pairing interactions in the ^1So channel for the bare NN interaction, Bonn potential and the Gogny effective interaction are obtained. It is found that the separable force of the Gogny effective interaction in the 1So channel has a clear link with the bare NN interaction. With such a simple separable form pairing properties provided by the Gogny force in nuclear matter can be reproduced.     

三阶色散影响下皮秒孤子间的相互作用

对色散位移光纤中三阶色散影响下皮秒孤子之间的相互作用进行数值计算,结果表明该类光纤中孤子之间的相互作用比常规光纤中严重,前者对通信系统性能的影响比后者更大。为此,本文还就色散位移光纤孤子间相互作用的抑制问题提出了新的建议。     

Soliton interaction in logarithmically saturable media

An analysis, based on the variational approach, is carried out of the interaction between two fully coherent solitons as well as two partially coherent soliton stripes in a medium with logarithmic nonlinearity. For the coherent case, it is found that the interaction can be both attractive and repulsive depending on the relative phase. The different interaction scenarios involve a bound system where the distance between the solitons oscillates with various magnitude of the oscillation amplitude, including total coalescence, and another where the solitons separate asymptotically. The effect of partial coherence on the soliton interaction is also studied by analyzing the interaction between two partially coherent soliton stripes. It is found that the strength as well as the character (attractive/repulsive) of the interaction changes for decreasing coherence. Thus, the general interaction properties of solitons in logarithmic nonlinear media are qualitatively similar to those of solitons in nonlinear Kerr media.     

Electron-TO-phonon interaction in polar crystals

In the present work, the interaction between electrons and long-wavelength transverse optical (TO) vibrations in a polar insulator is considered. The crystal model employed for the theoretical analysis includes classical potentials and electronic polarizabilities. A significant enhancement of the strength of the electron-TO-phonon interaction in ferroelectrics has been found. A microscopic justification of this effect is given. A bridge that relates the interaction of electrons with the polar long-wavelength TO modes of lattice vibrations to the long-range dipole-dipole interaction is established. As an application of our analysis, a novel method for quantitative predictions of the electron-TO-phonon interaction constants in polar crystals via the data of experimental studies is suggested.     

On the first order valence transition in SmS

The valence transition in SmS is investigated on the basis of a model which incorporates the Falicov-Kimball (F-K) interaction, f-d hybridization and electron-phonon interaction. We find that the transition is of first order even in the absence of electron-phonon interaction if the F-K interaction is sufficiently strong. Electron-phonon interaction makes the first order transition possible for a weaker F-K interaction. The effect is further enhanced if phonon-induced f-f and f-d coupling are simultaneously present. All calculations are done for finite temperature and the temperature dependence of the transition is found to be in agreement with the phase diagram of SmS.     

Non-local defect interaction in one-dimension: weak versus strong non-locality

Defect interaction (kink-antikink interaction) is studied for a prototypical model for non-local interaction. Mathematically, it is a bistable integrodifferential model, where the non-local interaction is performed due to an integral kernel. The system is able to establish domains where it is in one of its two equilibria, separated by defects. It is shown that the defect interaction depends on the asymptotical behavior of the integral kernel. In the weak non-local regime, when the integral kernel decays faster than an exponential at infinitum, the defect interaction is exponentially weak. Hence, this case is qualitatively similar to the local one. On the other hand, in the strong non-local regime, when the integral kernel decays slower than an exponential at infinitum, the defect interaction is ruled by the asymptotical behavior of the integral kernel. In this case, the defect interaction is stronger, and could be characterized, for instance, by a power law. The effect of this transition (from the weak to strong non-locality) on the domain dynamics is discussed.     

Interaction of parabolic-shaped pulse pair in a passively mode-locked Yb-doped fiber laser

We numerically investigate the formation and interaction of parabolic-shaped pulse pair in a passively mode-locked Yb-doped fiber laser. Based on a lumped model, the parabolic-shaped pulse pair is obtained by controlling the inter-cavity average dispersion and gain saturation energy, Moreover, pulse repulsive and attractive motion are also achieved with different pulse separations. Simulation results show that the phase shift plays an important role in pulse interaction, and the interaction is determined by the inter-cavity average dispersion and gain saturation energy, i.e., the strength of the interaction is proportional to the gain saturation energy, the stronger gain saturation energy will result in higher interaction intensity. On the contrary, the increase of the inter-cavity dispersion will counterbalance some interaction force. The results also show that the interaction of a parabolic-shaped pulse pair has a larger interaction distance compare to the conventional solitons.     

Interaction of a parabolic-shaped pulse pair in a passively mode-locked Yb-doped fiber laser

We numerically investigate the formation and interaction of a parabolic-shaped pulse pair in a passively mode-locked Yb-doped fiber laser. Based on a lumped model, the parabolic-shaped pulse pair is obtained by controlling the intercavity average dispersion and gain saturation energy, Moreover, pulse repulsive and attractive motion are also achieved with different pulse separations. Simulation results show that the phase shift plays an important role in pulse interaction, and the interaction is determined by the inter-cavity average dispersion and gain saturation energy, i.e., the strength of the interaction is proportional to the gain saturation energy, a stronger gain saturation energy will result in a higher interaction intensity. On the contrary, the increase of the inter-cavity dispersion will counterbalance some interaction force. The results also show that the interaction of a parabolic-shaped pulse pair has a larger interaction distance compared to conventional solitons.     

非线性两能级系统中的Landau-Zener-Coulomb跃迁

非线性跃迁动力学的研究是量子操控中的一个重要课题,在原子分子光物理、量子信息以及固体物理等领域都有着重要的应用.本文研究了具有粒子间相互作用两能级系统中的Landau-Zener-Coulomb跃迁动力学.结果表明,对于能级的斜率正负不同的情况,粒子间相互作用对系统跃迁动力学的影响完全不同.为正时,粒子间相互作用总是抑制能级间的非绝热跃迁,且相互作用强度越大,两能级间的非绝热跃迁越难发生.而为负时,弱相互作用会促进能级间的非绝热跃迁,在强相互作用情况下,跃迁概率会出现振荡.随着相互作用强度的增大,振荡幅度逐渐减小,能级间的非绝热跃迁受到抑制.     

On energy independent effective interactions in shell model calculations

It is shown, that the use of an energy independent effective interaction in a shell model calculation implies a strongly energy dependent residual interaction and thus a nucleon-nucleon interaction which is strongly energy dependent in the energy region of interest.     

Dispersion-managed soliton interactions in optical fibers

We simulated dispersion-managed soliton propagation and interaction in optical fibers. The energy-enhancement factor, together with the time-bandwidth product and the stretching factor, were calculated as a function of the difference in absolute values of accumulated dispersion in the fiber spans. The interaction strength of the dispersion-managed solitons was found to depend on the stretching factor. When this factor is less than 1.5, the interaction is weaker than for ideal solitons. When it is more than 1.5, there is a strong interaction between the pulses, which constrains the energy enhancement for practical applications.     

同位旋依赖的动量相关作用对同位旋分馏的影响随入射道条件的演化

由量子分子动力学通常应用的动量相关作用公式出发，引入同位旋自由度后得到了在量子分子动力学中可用于数值计算的同位旋依赖的动量相关作用.并用这个公式较系统地研究了在它的作用下，同位旋分馏比的入射道效应和它们的动力学机理.结果表明所有入射道能量、碰撞参数以及所有的丰中子碰撞系统中子-质子比和质量条件下动量相关作用的同位旋依赖性对同位旋分馏过程产生了重要的同位旋效应，然而它没有明显改变同位旋分馏比对于对称势灵敏的依赖性，即在考虑动量相关作用的同位旋自由度后同位旋分馏比仍是提取同位旋非对称核物质状态方程的灵敏探针. 关键词： 同位旋分馏比 动量相关作用 重离子碰撞     

Higher-order wave interactions in a periodic medium

A singular perturbation analysis of the interaction of the fundamental plane wave progressing in the direction of the sinusoidally varying permittivity of an unbounded medium with the first four space harmonics progressing in the reverse direction is carried out. The periodic inhomogeneity introduces self and mutual interaction phenomena. The self interaction, in general, produces a phase shift and causes the mutual interaction to occur for frequencies higher than those predicted by the Bragg condition. The mutual interaction introduces a complex change in the wavenumber resulting in the interacting waves becoming evanescent. Analytical expressions for the frequency shift and the other wave characteristics in the interaction region are deduced. With the increase in the order of the interaction, the frequency shift becomes a more dominant effect than the wave evanescence.     

Spin polarization in parallel double dots with spin-orbit interaction

Spin polarization in parallel double quantum dots embedded in arms of Aharonov-Bohm interferometer is investigated. The spin-orbit interaction exists in quantum dots. We find that the spin polarization is quite large even with a weak spin-orbit interaction. The direction and the strength of the spin polarization are well controllable and manipulatable by simply varying the strength of spin-orbit interaction or the energy levels in quantum dots. Moreover, electron-electron interaction strengthens the spin accumulation when the energy levels of the two quantum dots are identical. As the energy levels are unequal, electron-electron interaction cannot increase the spin accumulation. It is worth mentioning that the device is free of a magnetic field or a ferromagnetic material and it can be easily realized with present technology.     

Exciton-phonon interaction in cylindrical semiconductor quantum dots

The exciton-longitudinal optical phonon interaction is theoretically investigated for the case of polar semiconductor cylindrical quantum dots embedded in semiconductor matrix. The theory is developed within the dielectric continuum model considering the Fröhlich interaction between electrons and confined bulk longitudinal optical phonons for a configurational interaction model of quantum dot. Representative longitudinal optical phonon mode for the exciton-phonon interaction is predicted for cylindrical InAs/GaAs quantum dots.     

The symmetric and antisymmetric superexchange interactions in spin-Peierls system

The influences of Dzyaloshinskii Moriya （DM） interaction and Kaplan-Shekhtman-Entinwohlman-Aharony （KSEA） interaction on the dimerization of a spin-Peierls system are investigated theoretically by using the Lanczos numerical method. The ground state of the spin-Peierls system is still dimerized phase when both of the DM and the KSEA interactions have the same value with Heisenberg interaction. It is found that the KSEA interaction and uniform DM interaction are always against systemic dimerization, but the staggered DM interaction acts in favour of dimerization. Furthermore, the influences of the DM and the KSEA interactions are also studied in terms of the ground state index rate and the energy gap index rate of the dimerized Heisenberg system. The results show that the DM interaction makes the index rates larger, while the KSEA interaction makes them smaller.     

Quantum entanglement in an interacting electron gas

The entanglement between two electrons in a degenerate electron gas is studied as a function of their separation. We have taken into account the screened Coulomb interaction between electrons. It is found that interaction leads to a suppression of the entanglement distance. The interaction leads also to a direct dependence of entanglement distance on density.     

Nonlinear increase in bubbles radii caused by sound in a bubbly liquid

The nonlinear interaction of acoustic and entropy modes in a bubbly liquid is considered. The reasons for interaction are both nonlinearity and dispersion. In the field of intense sound, a decrease in the mixture density is predicted. That corresponds to the well-established growth of bubbles volumes due to rectified diffusion. The nonlinear interaction of modes as a reason for a bubble to grow due to sound, is discovered. The example considers variation in the mixture density and bubbles radii caused by acoustic soliton.