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.     

High-pressure equation of state for solid krypton from interatomic potentials

The pressure-volume isotherm for krypton at 300 K is evaluated by the Monte Carlo method using pair and three-body potentials. The pair potentials used are that of Aziz and Slaman and a slightly modified version of their potential which gives better agreement with high-energy scattering data. The three-body potentials considered are the Axilrod-Teller interaction and the first-order three-body exchange interaction as parametrized by Loubeyre. The results are compared with recent measurements at pressures up to 300 kbar and the implications of the comparison are discussed. The best agreement with experiment is found using the Axilrod-Teller interaction as the only many-body interaction, indicating that the three-body exchange interaction is to a large extent canceled by higher many-body interactions, at least in the highly symmetrical environment of the crystal.This paper is dedicted to Howard Reiss on the occasion of his 66th birthday.     

Microscopic theory of multiple scattering for open-shell nuclei

We consider the scattering of a distinguishable projectile from a nucleus assuming that the underlying interaction Hamiltonian is a sum of two-body potentials. We show that the effective interaction of the projectile with the nucleus in a truncated nuclear model space can be calculated as a linked-cluster expansion. The rules for evaluating this expansion are given in terms of the nucleon-nucleon and projectile-nucleon potentials and the exact eigenstates of the (effective) shell-model interaction. The shell-model interaction is required to be an energy-independent, Hermitian potential; its expression in terms of the underlying two-body potential is given by folded diagrams. The terms in the expansion of the effective projectile-nucleus interaction must also contain folded diagrams but, unlike the shell-model potential, these are energy-dependent in order to describe the singularities associated with the crossing of the scattering thresholds as the projectile energy is varied. Once the effective interaction is known, elastic and inelastic scatterings may be evaluated numerically by solving a finite-dimensional coupled-channel equation.     

Analytical solution of 1D Ising-like systems modified by weak long range interaction

It is well-known that 1D systems with only nearest neighbour interaction exhibit no phase transition. It is shown that the presence of a small long range interaction treated by the mean field approximation in addition to strong nearest neighbour interaction gives rise to hysteresis curves of large width. This situation is believed to exist in spin crossover systems where by the deformation of the spin changing molecules, an elastic coupling leads to a long range interaction, and strong bonding between the molecules in a chain compound leads to large values for nearest neighbour interaction constants. For this interaction scheme an analytical solution has been derived and the interplay between these two types of interaction is discussed on the basis of experimental data of the chain compound which exhibits a very large hysteresis of 50 K above RT at 370 K. The width and shape of the hysteresis loop depend on the balance between long and short range interaction. For short range interaction energies much larger than the transition temperature the hysteresis width is determined by the long range interaction alone. Received 26 November 1998     

Observation of the condensation of a gas of interacting grains

We consider an ensemble of grains that interact through a dipole-dipole interaction. A granular gas is formed by the vertical motion of a piston at the bottom boundary of the system. The interaction between the grains is controlled by an horizontally applied magnetic field. When the speed of the piston is decreased, we observe a transition from a low density to a high density phase. When the interaction between grains is weak, the transition is continuous. It is discontinuous for stronger interaction. The phase diagram displays strong similarities with the ones observed for usual equilibrium phase transitions.     

Two-pion exchange interaction between constituent quarks

The two-pion exchange interaction between constituent quarks is shown to enhance the effect of the isospin dependent spin-spin component of the one-pion exchange interaction, and to cancel out its tensor component. It therefore provides a partial explanation for the phenomenological observation that the hyperfine interaction between constituent quarks is well described by a flavor dependent spin-spin interaction, which is attractive at short and repulsive at long range. The spin-orbit component of the two-pion exchange interaction is stronger than and has the opposite sign from that associated with the linear confining interaction in the P-shell multiplets.     

光谱学研究血卟啉与鲱鱼精DNA的相互作用

以中性红(NR)作探针研究了血卟啉(HD)与DNA的相互作用.光谱学研究表明,血卟啉与DNA发生作用生成了超分子复合物.其结合比nHD:nDNA=3:1,血卟啉与DNA的结合常数K=1.84×104L/mol.同时运用Scatchart方程研究了血卟啉与DNA的作用方式,确定了血卟啉与鲱鱼精DNA之间的作用方式为混合作用方式.其作用机理可能是血卟啉以部分插入方式同时伴随共价和静电方式与DNA作用,影响其基因调控与表达,进而抑制肿瘤细胞的生长.     

Entanglement and Fidelity of a Spin Ladder with Dzyaloshinsky-Moriya Interaction

The spin ladder with Dzyaloshinsky-Moriya interaction is investigated by using the quantum renormalization-group method. The entanglement and fidelity are periodic functions of the time and oscillate between zero and one. The oscillation period decreases with either the interaction in the spin ladder or the
Dzyaloshinsky-Moriya interaction increasing. When the system relates to the environment, both entanglement and fidelity oscillate with a damping rate related to intrinsic decoherence rate, the interaction in the spin ladder, and the Dzyaloshinsky-Moriya interaction.     

Tuning the nonlocal spin-spin interaction between quantum dots with a magnetic field

We describe a device where the nonlocal spin-spin interaction between quantum dots (QDs) can be turned on and off with a small magnetic field. The setup consists of two QDs at the edge of two two-dimensional electron gases (2DEGs). The QDs' spins are coupled through a RKKY-like interaction mediated by the electrons in the 2DEGs. A magnetic field B(z) perpendicular to the plane of the 2DEG is used as a tuning parameter. When the cyclotron radius is commensurate with the interdot distance, the spin-spin interaction is amplified by a few orders of magnitude. The sign of the interaction is controlled by finely tuning B(z). Our setup allows for several dots to be coupled in a linear arrangement and it is not restricted to nearest-neighbor interaction.     

翼梢侧向喷流干扰特性数值模拟

当弹体表面安装喷管时,在喷管迎风条件下往往出现不利的侧向喷流干扰,翼梢安装喷管能减弱这种不利干扰.采用有限体积离散方法求解N-S方程,研究了旋成体-边条翼-舵组合体翼梢安装喷管的侧向喷流干扰特性和规律.分析了干扰流场结构和喷流干扰因子随Mach数、攻角、飞行高度等参数的变化特性.研究结果表明:翼梢喷流干扰形成了非常复杂的流场结构,虽然翼梢喷流远离弹体,仍对弹体、翼、舵上的载荷产生明显影响,在不同飞行条件下干扰范围和强度明显不同.喷流气动干扰因子规律复杂并呈非线性变化,干扰因子大于0.5的范围明显增加,有效增加了喷流控制使用范围.但在某些条件下仍然出现较大负值,产生严重不利干扰现象.      

Enhancing stationary optomechanical entanglement with the Kerr medium

We theoretically investigate the stationary entanglement of a optomechanical system with an additional Kerr medium in the cavity. There are two kinds of interactions in the system, photon-mirror interaction and photon-photon interaction. The optomechanical entanglement created by the former interaction can be effectively controlled by the latter one. We find that the optomechanical entanglement is suppressed by Kerr interaction due to photon blockage. We also find that the Kerr interaction can create the stationary entanglement and induce the resonance of entanglement in the small detuning regime. These results show that the Kerr interaction is an effective control for the optomechanical system.     

Effect of the three-atom interaction in magnetically dilute Ising systems

The dilute Ising ferromagnet with the three-atom interaction is studied by a new effective field theory based on Callen's identity. The initial slope of the Curie temperature with dilution is shown to be strongly affected by the presence of this interaction.     

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.     

Effects of electric field and size on the electron-phonon interaction in a spherical quantum dot with impurity

The effects of electric field and size on the electron-phonon interaction with an on-center impurity in a Zn_1?x Cd _x Se/ZnSe spherical quantum dot are studied, taking into account the interactions with confined, half-space and surface optical phonons. In addition, the interaction between impurity and phonons has also been considered. The results show that the electron-confined, electron-half-space, and electron-surface optical phonon interaction energies are all negative. The electron-confined optical phonon interaction energy is weakened by the electric field, but the electron-half-space and electron-surface optical phonon interaction energies are strengthened by it. In particular, the electron-surface optical phonon interaction depends strongly on the electric field, and it will vanish when the electric field is absent. It is also found that the electron-confined optical phonon interaction and electron-impurity “exchange” interaction energies reach a peak values as the quantum dot radius increases and then gradually decrease, but the electron-half-space optical phonon interaction energy exponentially quickly approaches 0 as the quantum dot radius increases.     

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.     

The Critical Behavior of the Antiferromagnetic Ising Model with Long-Range Interaction Effects

In this paper, the antiferromagnetic Ising model with ferromagnetic long-range interaction is modeled by the Monte Carlo method. The case of ferromagnetic long-range forces decreasing by a power law is considered. The dependence of the phase-transition temperature on long-range interaction parameters is obtained. The phase diagram was constructed at different values of long-range interaction parameters. Conditions for the existence of the frustrated state of the system were revealed.     

Laser-driven shock propagation into quartz targets driven by various drive pulse configurations: experiments

We theoretically investigate the atomic energy band of ultracold atoms inside a laser-driven optical cavity with Kerr medium. This cavity-atom hybrid system has two kinds of interactions: photon-atom interaction and photon-photon one. We find the loops of the atomic energy band induced by photon-atom interaction disappear when the Kerr interaction between photons exceeds a critical value. The reason of the controllably atomic energy band loops by Kerr interaction is discussed.     

The shot noise of a strongly correlated quantum dot coupled to the Luttinger liquid leads

We study the shot noise of a strongly correlated quantum dot weakly coupled to Luttinger liquid leads in the Kondo regime by means of the extended equation of motion method. A general zero-frequency shot noise formula with good convergence is derived. The shot noise exhibits a non-monotonic dependence on voltage for weak intralead interaction. There is a peak around the Kondo temperature at low voltage when the interaction is very weak, and its height decreases rapidly with the intralead interaction increasing. When the interaction is moderately strong the peak disappears and the shot noise scales as a power law in bias voltage, indicating that the intralead electron interaction suppresses the shot noise. It is possible that the measurements of the shot noise spectrum can extract the information of the intralead interaction.     

Effects of electron-interface-phonon interactions on interactions between electrons in double-heterostructures

Effects of electron-interface-phonon interaction on the interaction between electrons in double heterostructures are considered. It is found that the interaction potential between electrons caused by each of four interface-phonon modes is different. For electrons moving at the two interfaces of double heterostructure, the interaction energies of the electrons produced by the interaction with antisymmetric modes are positive which indicate that the forces between electrons are repulsive. The interaction energies caused by interaction with symmetric modes are negative and the forces are attractive. The resultant of the forces are attractive and become larger when the width of potential barrier decreases for InAs/GaSb/InAs double heterostructure.