量子棒中强耦合氢化杂质束缚磁极化子基态性质的磁场和温度依赖性

Magnetic field and temperature dependence of the properties of the ground state of the strong-coupling bound magnetopolaron in quantum rods(QRs) with hydrogenic impurity is studied by means of the Huybrechts-Lee -Low-Pines transformation method and the quantum statistical theory.The expressions for the ground-state energy and the mean number of phonons of the magnetopolaron are derived.Results of the numerical calculations show that the bound state of the magnetopolaron cannot be formed when the value of the aspect ratio of the QR,the dielectric constant ratio,the electron-phonon coupling strength or the temperature parameter is small.The larger the deviation of the value of aspect ratio e’from 1 is,the more it is unfavorable to the stability of the ground state of the magnetopolaron.When the magnetopolaron is in the bound state,the absolute value of its ground-state energy and its mean number of phonons increase with an increase of the dielectric constant ratio and confinement strength of QRs,but decrease with an increase in the cyclotron frequency of the external magnetic field and the temperature. The absolute value of the ground-state energy and the mean number of phonons of the magnetopolaron decrease with decreasing e’when e’<1,but decrease with increasing e’when e’>1.They get the maximum value at e’=1.     

抛物量子点中弱耦合束缚磁极化子的性质

采用线性组合算符和幺正变换方法研究了抛物量子点中弱耦合束缚磁极化子的振动频率和基态能量,并对其进行了数值计算。结果表明:束缚极化子的振动频率随有效受限长度的增加而减小,随库仑束缚势和回旋共振频率的增加而增加;束缚磁极化子的基态能量随有效受限长度、电子-体纵光学声子耦合强度、库仑束缚势的增加而减小,随回旋共振频率的增加而增加。     

量子棒中弱耦合杂质束缚极化子的性质

给出了具有椭球边界量子棒经过坐标变换成球形边界的哈密顿量。采用线性组合算符和幺正变换的方法,研究了在非均匀抛物限制势下量子棒中弱耦合杂质束缚极化子的振动频率、基态能量和基态结合能随库仑束缚势、电子-声子耦合强度和椭球的纵横比的变化关系。数值计算结果表明:振动频率、基态能量和基态结合能随库仑束缚势的增加而增大,基态能量和基态结合能随电子-声子耦合强度的增加而增加。当e′>1时,振动频率、基态能量和基态结合能随椭球的纵横比的增加而增加;e′<1时,随纵横比的减少,振动频率、基态能量和基态结合能都增大;当e′=1时,振动频率取极小值,基态能量和基态结合能也取较小的稳定值。     

Effect of a magnetic field on the energy levels of donor impurities in the ZnO parabolic quantum well

Energy levels of a donor impurity in the ZnO parabolic quantum well under the magnetic field are investigated using the variational method.The binding energy of the ground state,the energies of 2p±state and 1 s→2p±transition energies of a hydrogenic donor in the ZnO parabolic quantum well are numerically calculated as a function of the strength of magnetic field for different parabolic potential fields.The results show that the external magnetic field has an obvious influence on the binding energies and the 1 s→2p±transition energies of a hydrogenic donor.The Is to 2p±transition energy increases linearly with the strength of magnetic field,but the Is to 2p_ transition energy decreases when the strength of magnetic field increases for the small field strength. Compared to the GaAs parabolic well,the donors are more tightly bound to the ZnO parabolic well and the influence of external magnetic field on the binding energy of a donor is much stronger in the ZnO parabolic well.     

非对称量子点中杂质束缚极化子性质

采用线性组合算符和幺正变换方法,研究磁场对非对称量子点中弱耦合杂质束缚极化子性质的影响。导出了非对称量子点中弱耦合杂质束缚磁极化子振动频率和基态结合能随量子点的横向和纵向受限强度、磁场的回旋共振频率、库仑束缚势和电子-声子耦合强度的变化关系。数值计算结果表明:非对称量子点中弱耦合杂质束缚磁极化子振动频率和基态结合能随量子点的横向和纵向受限强度的增大而迅速增大,表现出奇特的量子尺寸效应。     

在磁场作用下氮化物抛物量子阱中杂质态能量

采用变分法研究了在外磁场作用下GaN／AlxGa1-xN无限抛物量子阱（PQW）中类氢杂质态能级，给出不同磁场下杂质态基态能、结合能随阱宽的变化关系以及能量随磁场强度变化的函数关系。数值结果表明：外磁场对类氢杂质能量和结合能均有明显的影响，杂质态能量随磁场的增强而显著增大，并且随阱宽的增大而增大；GaN／Al0.3Ga0.7 N PQW对杂质态的束缚程度比GaAs／Al0.3Ga0.7As PQW强。     

量子棒中弱耦合极化子的基态能量

The Hamiltonian of the quantum rod （QR） with an ellipsoidal boundary is given after a coordinate transformation. Using the linear-combination operator and unitary transformation methods, the vibrational frequency and the ground-state energy of weak-coupling polarons are obtained. Numerical results illustrate that the vibrational frequency increases with the decrease of the effective radius R0 of the ellipsoidal parabolic potential and the aspect ratio e of the ellipsoid, and that the ground-state energy increases with the decrease of the effective radius R0 and the electron-LO-phonon coupling strength α. In addition, the ground-state energy decreases with increasing aspect ratio e within 0 〈 e 〈 1 and reaches a minimum when e = 1, and then increases with increasing e for e 〉 1.     

抛物量子点中弱耦合杂质束缚磁极化子的光学声子平均数

采用线性组合算符和幺正变换方法研究库仑场对抛物量子点中弱耦合杂质束缚磁极化子的振动频率和光学声子平均数的影响。导出量子点中弱耦合杂质束缚磁极化子的振动频率和光学声子平均数随量子点的有效受限长度、库仑束缚势和磁场的回旋共振频率的变化关系。数值计算结果表明：弱耦合杂质束缚磁极化子的振动频率和光学声子平均数随量子点的有效受限长度的减小而迅速增大,表现出奇特的量子尺寸效应。随磁场的回旋共振频率和库仑束缚势的增加而增加。     

量子线中弱耦合束缚磁极化子激发态的性质

从电子与体纵光学声子(LO声子)体系的哈密顿量出发,采用Huybrenchts的线性组合算符及幺正变换方法研究了在磁场作用下抛物量子线中弱耦合束缚极化子的激发能量、第一内部激发态能量和振动频率,并对其进行了数值计算,数值计算结果表明:抛物量子线中弱耦合束缚磁极化子的第一内部激发态能量随库仑束缚势的增加而减少,随约束强度...     

Highly Bright and Compact Alloyed Quantum Rods with Near Infrared Emitting: a Potential Multifunctional Nanoplatform for Multimodal Imaging In Vivo

Controlling synthesis of near‐infrared emitting quantum rods (QRs) for in vivo imaging is a major challenge in the fabrication of multifunctional nanoprobes. Here, a reliable synthetic approach for CdTe _x Se_1–x /ZnS alloy nanocrystals to achieve highly bright (quantum yields up to 80%) with controllable rod‐shape and near‐infrared (650–870 nm) emission is developed. Aspect ratio and emission of QRs are correlated with composition, which can be easily tuned by changing Te and Se mole ratio. It illustrates that the content of Se plays an important role in maintaining the rod‐shape, while Te has a significant impact on emitting of the nanorods. Besides exhibiting great stability over a broad range of pH (4–10) and ion strength (up to 2 mol L^‐1 NaCl solution), these hydrophilic QRs display good photo stability and storage stability. In particular, the specially absorbing of paramagnetic gadolinium ions on the QRs lead to a versatile method to engineer multimodal imaging nanoprobes, which are applied for in vivo lymph node dual‐modal imaging (fluorescence and magnetic resonance imaging). These results suggest a promising strategy for engineering multifunctional imaging nanoprobes with the stable near‐infrared QRs.     

声子之间相互作用对半导体量子点中磁极化子性质的影响

研究了半导体量子点中磁极化子的性质.采用线性组合算符和微扰法,导出了半导体量子点中磁极化子的基态能量.在计及电子在反冲效应中发射和吸收不同波矢的声子之间相互作用时,讨论了对半导体量子点中磁极化子的基态能量的影响.通过数值计算表明,半导体量子点中磁极化子的基态能量随量子点的有效受限长度的减小而迅速增大,随磁场的增加而增加,对于弱磁场声子之间相互作用的影响不能忽略.     

自旋对量子点中束缚磁极化子性质的影响

采用线性组合算符和幺正变换方法,研究了自旋对量子点中弱耦合束缚磁极化子性质的影响。考虑自旋影响时,讨论了束缚磁极化子的基态能量随量子点受限长度和磁场的变化关系。结果表明:在库仑束缚势保持不变时,磁极化子的基态能量、自旋向上(向下)分裂能都随量子点受限长度的增大而减小,随磁场的增大而增大;在磁场保持不变时,磁极化子基态能量、自旋向上(向下)分裂能都随库仑束缚势的增大而减小。     

磁场和库仑场对量子点中强耦合束缚极化子性质的影响

采用线性组合算符和幺正变换方法研究了磁场和库仑场对半导体量子点中强耦合极化子性质的影响.导出了强耦合束缚磁极化子的振动频率和基态能量与量子点的有效受限长度、库仑束缚势、磁场的回旋共振频率和电子-声子耦合强度的变化关系.数值计算结果表明:强耦合束缚磁极化子的振动频率和基态能量随量子点的有效受限长度的减小而迅速增大,随磁场的回旋共振频率的增加而增大.基态能量随电子-声子耦合强度和库仑束缚势的增加而减少.     

Influence of strain on hydrogenic impurity states in a GaN/AlxGa1?xN quantum dot

Within the effective-mass approximation, we calculated the influence of strain on the binding energy of a hydrogenic donor impurity by a variational approach in a cylindrical wurtzite GaN/Al _x Ga_1−x N strained quantum dot, including the strong builtin electric field effect due to the spontaneous and piezoelectric polarization. The results show that the binding energy of impurity decreases when the strain is considered. Then the built-in electric field becomes bigger with the Al content increasing and the binding energy of hydrogenic donor impurity decreases when the Al content is increasing. For dot height L < 2 nm, the change of the binding energy is very small with the Al content variety. This work has been supported by the National Natural Science Foundation of China (No. 10564003) and the Key Project of the Science and Technology Research of the Educational Ministry of China (No. 208025)     

库仑场对量子点中极化子性质的影响

采用基于逐次正则变换的变分方法,利用单模压缩态变换处理包含声子产生湮灭算符的双线性项,研究了抛物量子点中束缚极化子的性质. 得到了在电子-体纵光学声子强﹑弱耦合极限下抛物量子点束缚极化子的基态能量及电子周围平均声子数. 讨论了受限长度,电子-体纵光学声子耦合常数,库仑结合参数与基态能量和平均声子数之间的依赖关系.     

在外电场作用下有限抛物量子阱中类氢杂质态结合能

采用变分方法研究GaAs/AlxGa1-xAs有限抛物量子阱中类氢杂质态能量和结合能随外电场和阱宽的变化关系.在计算中考虑了电子有效带质量和介电常数随空间坐标(或合金组分)的变化因素.结果表明,外电场对类氢杂质态能量和结合能均有明显的影响,并且这些影响随着阱宽的增大而增大.电子有效带质量和介电常数随空间坐标的变化效应使得类氢杂质态基态能量减小,结合能增大,此效应随着阱宽的增大明显变小.     

Magnetic properties of donors in GaAsP

The magnetic properties of hydrogenic Te donors and bistable,DX-like S donors in GaAS _x P_1-x have been investigated. Te shows an EPR signal after cooling down, both in the dark. The EPR signal from S appears only after illumination. S does not show an EPR signal after cooling down in the dark, but after illumination when the hydrogenic state of this donor is populated. Static magnetic susceptibility measurements show however that the ground state of S in GaAs _x P_1-x is paramagnetic even though it does not produce an EPR signal. This is in agreement with a one-electron ground state of this bistable donor.     

库仑场对量子点中极化子性质的影响

采用基于逐次正则变换的变分方法,利用单模压缩态变换处理包含声子产生湮灭算符的双线性项,研究了抛物量子点中束缚极化子的性质. 得到了在电子-体纵光学声子强﹑弱耦合极限下抛物量子点束缚极化子的基态能量及电子周围平均声子数. 讨论了受限长度,电子-体纵光学声子耦合常数,库仑结合参数与基态能量和平均声子数之间的依赖关系.     

Effects of magnetic field on the polaron in an asymmetrical Gaussian confinement potential quantum well

The effects of a magnetic field on the vibrational frequency, the ground state energy and the ground state binding energy of a weak-coupling polaron in asymmetrical Gaussian confinement potential quantum well (AGCPQW) are investigated by using linear combination operator and unitary transformation methods.Our calculated results show that the vibrational frequency increases with increasing cyclotron frequency of the magnetic field;meanwhile, the absolute value of the ground state energy and the ground state binding energy decrease.The vibrational frequency, the absolute value of the ground state energy and the ground state binding energy are increasing functions of the barrier height of the AGCPQW.It is shown that the barrier height of the AGCPQW and the magnetic field are important factors that influence the properties of the magnetopolaron in AGCPQW.     

量子棒中杂质极化子的内部激发态

通过坐标变换把量子棒的哈密顿量由椭球边界变为球形边界.采用线性组合算符和么正变换方法研究了量子棒中弱耦合杂质极化子的第一内部激发态能量、激发能量和从第一内部激发态到基态跃迁频率随量子棒的横向和纵向有效受限长度、库仑束缚势、椭球的纵横比的变化关系.结果表明:它们随库仑束缚势的增加而增大,随纵横比和有效受限长度的增加而减少.表现出量子棒珍奇的量子尺寸限制效应.