声子之间相互作用对量子点中极化子性质的影响

研究了抛物量子点中弱耦合极化子的性质。采用线性组合算符和微扰法,导出了抛物量子点中极化子的基态能量。当计及电子在反冲效应中发射和吸收不同波矢的声子之间的相互作用时,讨论了对量子点中极化子的基态能量的影响。通过数值计算,结果表明,量子点中极化子基态能量随量子点的有效受限长度的减小而迅速增大,随电子-LO声子的耦合强度的增加而减少。当l₀>1.4时,声子之间的相互作用不能忽略。     

无限深量子阱中强耦合极化子的基态结合能

研究了无限深量子阱中极化子的基态性质,采用线性组合算符和变分相结合的方法导出了强耦合极化子的振动频率λ、基态能量E₀和基态结合能E_b,讨论了阱宽L和电子-LO声子耦合强度α对强耦合极化子的振动频率λ、基态能量E₀和基态结合能E_b的影响。通过数值计算,结果表明:强耦合极化子的振动频率和基态结合能随阱宽L的增大而减小,随电子-LO声子耦合强度α的增强而增大;基态能量随阱宽L的增大而减小,其绝对值随电子-LO声子耦合强度α的增强而增大;当量子阱阱宽L趋近于无限大和无限小两种极限情况下,分别与三维和二维极化子的结果相一致。     

抛物量子点中强耦合磁极化子的性质

采用Pekar类型的变分方法研究了抛物量子点中强耦合磁极化子的基态和激发态的性质。计算了基态和激发态磁极化子的束缚能以及磁极化子的共振频率。讨论了这些量对回旋频率和有效限制强度的依赖关系,以及磁极化子光学声子平均数的性质,结果表明:由于Zeeman劈裂,抛物量子点中磁极化子的回旋共振频率劈裂为两支。基态和激发态磁极化子的束缚能以及磁极化子的共振频率都随回旋频率的增加而增大,随量子点的有效束缚强度的增大而减小。     

Vortex lattices in rotating atomic bose gases with dipolar interactions

We show that dipolar interactions have dramatic effects on the ground states of rotating atomic Bose gases in the weak-interaction limit. With increasing dipolar interaction (relative to the net contact interaction), the mean field, or high filling factor, ground state undergoes a series of transitions between vortex lattices of different symmetries: triangular, square, "stripe," and "bubble" phases. We also study the effects of dipolar interactions on the quantum fluids at low filling factors. We show that the incompressible Laughlin state at filling factor nu = 1/2 is replaced by compressible stripe and bubble phases.     

抛物阱中极化子效应对D-心的影响

采用改进的LLP方法在考虑体声子影响的情况下研究了抛物量子阱中电子-LO声子相互作用对D^-心能量的影响.研究结果表明,阱宽较小时,D^-心的基态能量和结合能随着阱宽L的增大而急剧减小;阱宽较大时,能量的减小比较缓慢,最后接近体材料中的三维值.并且得出了电子-LO声子相互作用可使D^-心的结合能有显著的提高.     

抛物量子点中弱耦合磁极化子的性质

应用线性组合算符和幺正变换方法研究了抛物量子点中磁极化子的基态性质。得出基态能和基态束缚能随有效束缚强度增大而减小,随回旋频率增大而增大。当有效柬缚强度给定,基态能量随电子-体纵光学声子耦合强度增加而减小。当有效束缚强度l0>0.3时,电子-体纵光学声子耦合强度的变化对量子点中弱耦合磁极化子的基态能量的影响变得显著。当有效束缚强度l0<0.3时,电子-体纵光学声子耦合强度的变化对基态能量影响很小。由于有效束缚强度与量子点受限强度的平方根成反比,所以量子点受限越强,基态能量、基态束缚能越大,电子一体纵光学声子耦合强度和磁场的变化对量子点的影响相对越小;当量子点受限变弱时,电子-声子耦合强度变化对量子点的影响变大,磁场对量子点的影响也变大,所以在量子点中,极化子对量子点的影响不容忽略。     

Effects of Shannon entropy and electric field on polaron in RbCl triangular quantum dot

In this paper, the time evolution of the quantum mechanical state of a polaron is examined using the Pekar type variational method on the condition of the electric-LO-phonon strong-coupling and polar angle in RbCl triangular quantum dot. We obtain the eigenenergies, and the eigenfunctions of the ground state, and the first excited state respectively. This system in a quantum dot can be treated as a two-level quantum system qubit and the numerical calculations are performed.The effects of Shannon entropy and electric field on the polaron in the RbCl triangular quantum dot are also studied.     

Energy of a Polaron in a Wurtzite Nitride Finite Parabolic Quantum Well

The effects of electron-phonon interaction on energy levels of a polaron in a wurtzite nitride finite parabolic quantum well （PQW） are studied by using a modified Lee-Low-Pines variational method. The ground state, first excited state, and transition energy of the polaron in the GaN/Al0.3Ga0.7N wurtzite PQW are calculated by taking account of the influence of confined LO（TO）-like phonon modes and the half-spaee LO（TO）-like phonon modes and considering the anisotropy of all kinds of phonon modes. The numerical results are given and discussed. The results show that the electron-phonon interaction strongly affects the energy levels of the polaron, and the contributions from phonons to the energy of a polaron in a wurtzite nitride PQW are greater than that in an A1GaAs PQW. This indicates that ehe electron-phonon interaction in a wurtzite nitride PQW is not negligible.     

Selective preparation of ground state wave-packets: a theoretical analysis of femtosecond pump-dump-probe experiments on the potassium dimer

We present simulations on pump-dump-probe experiments performed on the potassium dimer. The interaction of two time-delayed laser pulses prepares vibrational wave packets in the electronic ground state. The quantum calculations reveal to what extent it is possible to prepare a ground state superposition of states with high versus low vibrational quantum numbers by changing the pump-dump delay time. It is shown that transient signals may exhibit interference effects which are due to characteristics of ground state wave-packets composed of two components showing different vibrational dynamics. In this way the signals are able to yield information about vibrational overtone motion. Received 27 September 2000 and Received in final form 21 November 2000     

The electronic structure of a quantum well under an applied electric field

The effects of an applied electric field on quantum well subband energies are calculated variationally within the effective mass approximation for model potential profiles. The concept of a quasi-bound state is examined critically. For higher electric field values it is shown that the quasi-bound state approximation for the ground and first excited state of the electron, and for the ground state of the hole is valid.     

半导体量子阱中弱耦合磁极化子的性质

采用线性组合算符和改进的LLP变分法,研究了在考虑电子自旋情况下无限深量子阱中弱耦合磁极化子的性质。导出了弱耦合磁极化子的声子平均数、基态能量和电子自旋能量与磁极化子基态能量之比的绝对值的表达式。并对两种不同阱材料的量子阱进行了数值计算,结果表明:磁极化子的声子平均数随电子-LO声子耦合常数和阱宽的增加而增大,并且最终随着阱宽的增加而趋于体情况下的极限值;由于电子自旋能的作用使磁极化子的基态能量由不考虑电子自旋下的一条分裂为两条,并且它随阱宽和电子-LO声子耦合常数的增加而减小,随回旋共振频率(磁场)的增加而增大。电子自旋作用能否忽略由回旋共振频率和阱材料本身的性质决定。     

Polaronic effects in a polar semiconductor quantum strip with transverse parabolic confinement

The effect of electron–phonon interaction on the ground and excited state energies of an electron in a polar quantum strip is studied by using a variational method. It is shown that polaronic effects are quite significant and also size-dependent if the effective width of the strip is reduced below a certain value. It is also shown that the longitudinal polaron effective mass is substantially renormalized even by the transverse confinement in a quantum strip.     

The energy levels of a two-electron two-dimensional parabolic quantum dot

This paper studies the two-electron total energy and the energy of the electron--electron interaction by using a variational method of Pekar type on the condition of electric--LO-phonon strong coupling in a parabolic quantum dot. It considers the following three cases: 1) two electrons are in the ground state; 2) one electron is in the ground state, the other is in the first-excited state; 3) two electrons are in the first-excited state. The relations of the two-electron total energy and the energy of the electron--electron interaction on the Coulomb binding parameter, the electron-LO-phonon coupling constant and the confinement length of the quantum dot are derived in the three cases.     

Influence of excited Landau levels on a two-dimensional electron-hole system in a strong perpendicular magnetic field

The study of the quantum states of a two-dimensional electron-hole system in a strong perpendicular magnetic field is carried out with special attention to the influence of virtual quantum transitions of interacting particles between the Landau levels. These virtual quantum transitions from the lowest Landau levels to excited Landau levels with arbitrary quantum numbers n and m and their reversion to the lowest Landau levels in second order perturbation theory result in an indirect attraction between the particles. The influence of the indirect interaction on the magnetoexciton ground state, on the chemical potential of the Bose-Einstein condensed magnetoexcitons, and on the ground state energy of the metallic-type electron-hole liquid is investigated in the Hartree-Fock approximation. The coexistence of different phases is suggested.     

声子对隧穿量子点分子辐射场系统量子相位的影响

用全量子理论导出隧穿量子点分子-辐射场相互作用系统状态满足的微分方程组, 在相干态辐射场和量子点分子处于隧穿激发态及基态的初始条件下, 应用Pegg-Barnett相位理论计算和分析了辐射场的相位概率分布及相位涨落, 研究了声子-量子点分子作用对辐射场相位的影响, 并与Husimi相位分布做了比较. 结果表明, 温度显著影响光场相位概率分布的时间演化规律, 声子既可以抑制也可以增强辐射场相位扩散和涨落, 取决于量子点分子的初态. Husimi相位分布和Pegg-Barnett相位分布符合度相当高. 关键词： 量子点分子 声子 量子相位 Q函数')" href="#">Q函数     

量子点中强耦合极化子的性质

采用Pekar类型的变分方法研究了抛物量子点中强耦合极化子的基态和激发态的性质。计算了基态和激发态极化子的结合能、光学声子平均数和极化子的共振频率。讨论了这些量对有效限制强度和电子 体纵光学声子耦合强度的依赖关系。结果表明:抛物量子点中极化子的共振频率、基态和激发态极化子的结合能以及光学声子平均数都随量子点的有效束缚强度的增大而减小。光学声子平均数随电子 体纵光学声子耦合强度的增加而增大。     

The influence of electric field on a parabolic quantum dot qubit

This paper calculates the time evolution of the quantum mechanical state of an electron by using variational method of Pekar type on the condition of electric--LO-phonon strong coupling in a parabolic quantum dot. It obtains the eigenenergies of the ground state and the first-excited state, the eigenfunctions of the ground state and the first-excited state This system in a quantum dot may be employed as a two-level quantum system qubit. The superposition state electron density oscillates in the quantum dot with a period when the electron is in the superposition state of the ground and the first-excited state. It studies the influence of the electric field on the eigenenergies of the ground state, the first-excited state and the period of oscillation at the different electron--LO-phonon coupling constant and the different confinement length.     

Ground state phase diagram of a spin-2 antiferromagnet on the square lattice

We use the vertex state model approach to construct optimum ground states for a large class of quantum spin-2 antiferromagnets on the square lattice. Optimum ground states are exact ground states of the model which minimize all local interaction operators. The ground state contains two continuous parameters and exhibits a second order phase transition from a disordered phase with exponentially decaying correlation functions to a Néel ordered phase. The behaviour is very similar to that of the corresponding ground state of a quantum spin-3/2 model on the hexagonal lattice, which has been investigated in an earlier paper. Received 8 April 1999     

稳恒电、磁场中量子阱内极化子的基态能量

采用Ｌａｒｓｅｎ谐振子算符代数运算与变分波函数相结合的方法，研究处于与生长轴方向平行的稳恒电、磁场中量子阱内的电子——体纵光学声子相互作用系统。得到系统包括二级微扰修正的、作为量子阶宽度、电子－声子耦合常数以及电、磁场强度函数的基态能量表达式。结果表明：对电子基态能量的极化影响，随阱宽及电场强度的增大而减弱，而随磁场强度的增大而增强。 关键词：     

外电场作用下纤锌矿氮化物抛物量子阱中极化子能级

The energy levels of a polaron in a wurtzite nitride finite parabolic quantum well (PQW)are studied by a modified Lee-Low-Pines variational method. The ground state of the polaron, the transition energy from first exited state to the ground state and the 关键词： 氮化物抛物量子阱 电子-声子相互作用 极化子