离子掺杂钙钛矿量子点玻璃研究进展

近年来,全无机钙钛矿量子点因其优异的光电性能受到研究者的广泛关注,但其较差的稳定性极大地限制了其应用。利用玻璃优异的稳定性,控制钙钛矿量子点在玻璃中原位析出,使玻璃包覆在钙钛矿量子点周围,隔绝其与外界环境的接触,有效地提高了其稳定性。通过在钙钛矿量子点玻璃中掺杂特定的离子可以调控钙钛矿量子点的析晶情况和发光峰位,并可引入新的发光中心。本文根据掺杂离子的目的,综合介绍了离子掺杂钙钛矿量子点玻璃的研究进展,为近期关于离子掺杂钙钛矿量子点玻璃的研究提供了思路和参考。     

量子点量子阱中的三阶非线性光学特性的研究

利用紧致密度矩阵近似方法，研究了一个特殊量子点量子阱中的三阶非线性光学特性(三次谐波产生)，得到了量子点量子阱系统的三次谐波产生系数的解析表达式，而且考虑了量子点量子阱系统中的两种电子束缚态-壳层阱内与阱外两种束缚态。对CdS/HgS构成的典型的量子点量子阱进行了数值计算，得到了10^-15(m／v)^2量级的三次谐波产生系数，并且绘出了三次谐波产生系数作为量子点量子阱的尺寸和泵浦光子能量的函数曲线，最后对曲线的特征及其形成的原因进行了解析。     

Mn掺杂ZnSe量子点变温发光性质研究

量子点(QD)照明器件中电流导致的焦耳热会使其工作温度高于室温,因此研究量子点的发光热稳定性十分重要。本文利用稳态光谱和时间分辨光谱研究了具有不同壳层厚度的Mn掺杂ZnSe(Mn: ZnSe)量子点的变温发光性质,温度范围是80～500 K。实验结果表明,厚壳层(6.5单层(MLs))Mn: ZnSe量子点的发光热稳定性要优于薄壳层(2.6 MLs)的量子点。从80 K升温到400 K的过程中,厚壳层Mn: ZnSe量子点的发光几乎没有发生热猝灭,发光量子效率在400 K高温下依然可以达到60%。通过对比Mn: ZnSe量子点的变温发光强度与荧光寿命,对Mn: ZnSe量子点发光热猝灭机制进行了讨论。最后,为了研究Mn: ZnSe量子点的发光热猝灭是否为本征猝灭,对具有不同壳层厚度的Mn: ZnSe量子点进行了加热-冷却循环(300-500-300 K)测试,发现厚壳层的Mn: ZnSe量子点的发光在循环中基本可逆。因此,Mn: ZnSe量子点可以适用于照明器件,即使器件中会出现不可避免的较强热效应。     

玻璃中的半导体量子点

介绍了玻璃中的半导体量子点。对玻璃中半导体量子点的生长过程、量子的电子态，量子尺寸效应、库仑阻塞效应及介电效应，做了比较全面的介绍。讨论了量子点的应用及发展前景。     

单量子点在连续外场激发下发射光子性质的理论研究

用最近所发展的产生函数(generatingfunction)理论方法研究了单量子点在连续外场作用下光子发射的性质:光子发射强度,MandelQ参数以及X与Y偏振光子之间的关联〈NxNy〉在不同激发场强下随激发光场偏振方向的变化性质:在弱场激发下,激发场的强度决定了发射光子的特性;在强光场激发下,发射光子,MandelQ参数和X偏振以及Y偏振光子的关联〈NxNy〉都表现出比较复杂的非线性现象.     

隧穿量子点分子模型与光场相互作用的量子信息保真度

利用全量子理论和数值计算方法,研究隧穿量子点分子模型与光场相互作用的量子信息保真度,通过计算机模拟出量子点分子、光场和系统的保真度随时间的演化图像,分析了压缩系数和失谐量对量子信息保真度的影响.结果表明：改变初始光场的压缩系数和失谐量能调节相互作用系统的量子信息保真度.     

量子点间Kondo效应的遥控

利用GaAs/AlGaAs异质结二维电子所可以构成量子点 ,而门电极可以控制量子点内的电子数 .当量子点内具有奇数个电子 ,未配对电子的自旋磁矩有可能被来自源和漏极的电子云屏蔽 ,以致于整体上表现为一个无磁的“准点” .此时 ,从源极企图进入准点的电子 ,其隧穿几率将突增 ,在实验     

耦合量子点的三阶非线性光学特性

本文研究了两个耦合的圆型量子点的三阶光学非线性,并且利用密度矩阵算符理论导出了三次谐波产生的表达式.最后,以GaAs耦合量子点为例作了数值计算,并绘出了三次谐波产生与耦合量子点中的电子数以及光子能量之间的依赖关系.     

抛物线性限制势量子点量子比特及其光学声子效应

在抛物量子点中电子与体纵光学声子强耦合的条件下,应用Peaker变分方法得出了电子的基态和第一激发态的本征能量及基态和第一激发态本征波函数.量子点中这样的二能级体系可作为一个量子比特.当电子处于基态和第一激发态的叠加态时,计算出电子在空间的概率分布作周期性振荡.并且得出了振荡周期随受限长度及耦合强度的变化关系. 关键词： 量子点 量子信息 量子比特     

A Polaron in a Quantum Dot Quantum Well

The polaron effect in a quantum dot quantum well (QDQW)system is investigated by using the perturbation method. Both the bound electron states outside and inside the shell well are taken into account . Numerical calculation on the CdS/HgS QDQW shows that the phonon correction to the electron ground state energy is quite significant and cannot be neglected.     

单量子点微腔激光器的研究

研究一个三能级量子点耦合到单模光学腔组成的系统,该单量子点激光器的泵浦阈值较小,激光能较快地达到稳定输出,当量子点和腔模耦合强度增强时,其泵浦阈值更小,激光达到稳定输出的速度更快。     

Heat Generation by Electric Current in a Quantum Dot Molecular Coupled to Ferromagnetic Leads

We study the properties of the heat flow generated by electric current in a quantum dot(QD) molecular sandwiched between two ferromagnetic leads. The heat is exchanged between the QD and the phonon reservoir coupled to it. We find that when the leads' magnetic moments are in parallel configuration, the total heat generation is independent on the leads' spin-polarization regardless of the magnitude of the intradot Coulomb interaction. This behavior is similar to that of the electronic current. In the antiparallel configuration, however, the influences of the leads' ferromagnetism on the heat generation are quite different from those on the electric current. Under the conditions of weak intradot Coulomb interaction and small bias voltage, the heat generation is monotonously suppressed by increasing leads' spin-polarization.Whereas for sufficient large intradot Coulomb interaction and bias voltage, the heat generation shows non-monotonous behavior due to the electron-phonon interaction and the spin accumulation induced on the dot. Furthermore, the magnitude of the negative differential of the heat generation previously found in a QD connected to nonmagnetic leads can be weakened by the increase of the spin-polarization of the ferromagnetic leads.     

Heat Generation by Electric Current in a Quantum Dot Molecular Coupled to Ferromagnetic Leads

We study the properties of the heat flow generated by electric current in a quantum dot (QD) molecular sandwiched between two ferromagnetic leads. The heat is exchanged between the QD and the phonon reservoir coupled to it. We find that when the leads' magnetic moments are in parallel configuration, the total heat generation is independent on the leads' spin-polarization regardless of the magnitude of the intradot Coulomb interaction. This behavior is similar to that of the electronic current. In the antiparallel configuration, however, the influences of the leads' ferromagnetism on the heat generation are quite different from those on the electric current. Under the conditions of weak intradot Coulomb interaction and small bias voltage, the heat generation is monotonously suppressed by increasing leads' spin-polarization. Whereas for sufficient large intradot Coulomb interaction and bias voltage, the heat generation shows non-monotonous behavior due to the electron-phonon interaction and the spin accumulation induced on the dot. Furthermore, the magnitude of the negative differential of the heat generation previously found in a QD connected to nonmagnetic leads can be weakened by the increase of the spin-polarization of the ferromagnetic leads.     

The Electron-Hole Pair in a Single Quantum Dot and That in a Vertically Coupled Quantum Dot

The energy spectra of low-lying states of an exciton in a single and a vertically coupled quantum dots arestudied under the influence of a perpendicularly applied magnetic field. Calculations are made by using the method ofnumerical diagonalization of the Hamiltonian within the effective-mass approximation. We also calculated the bindingenergy of the ground and the excited states of an exciton in a single quantum dot and that in a vertically coupledquantum dot as a function of the dot radius for different values of the distance and the magnetic field strength.     

Large Negative Differential of Heat Generation in a Two-Level Quantum Dot Coupled to Ferromagnetic Leads

Heat current exchanged between a two-level quantum dot (QD) and a phonon reservoir coupled to it is studied within the nonequilibrium Green's function method. We consider that the QD is connected to the left and right ferromagnetic leads. It is found that the negative differential of the heat generation (NDHG) phenomenon, i.e., the intensity of the heat generation decreases with increasing bias voltage, is obviously enhanced as compared to that in single-level QD system. The NDHG can emerge in the absence of the negative differential conductance of the electric current, and occurs in different bias voltage regions when the magnetic moments of the two leads are arranged in parallel or antiparallel configurations. The characteristics of the found phenomena can be understood by examining the change of the electron number on the dot.     

The Electron－Hole Pair in a Single Quantum Dot and That in a Vertically Coupled Quantum Dot

The energy spectra of low-lying states of an exciton in a single and a vertically coupled quantum dots are studied under the influence of a perpendicularly applied magnetic field. Calculations are made by using the method of numerical diagonalization of the Hamiltonian within the effective-mass approximation. We also calculated the binding energy of the ground and the excited states of an exciton in a single quantum dot and that in a vertically coupled quantum dot as a function of the dot radius for different vaJues of the distance and the magnetic field strength.     

Effect of the Electron-LO-Phonon Coupling on an Exciton Quantum Dot

The influence of the electron-LO-phonon coupling on energy spectrum of the low-lying states ofan exciton inparabolic quantum dots is investigated as a function of dot size. Calculations are made by using the method of few-bodyphysics within the effective-mass approximation. A considerable decrease of the energy in the stronger confinement rangeis found for the low-lying states of an exciton in quantum dots, which results from the confinement of electron-phononcoupling.     

Quasi-Conical Quantum Dot: Electron States and Quantum Transitions

The exactly solvable model of quasi-conical quantum dot, having a form of spherical sector, is proposed. Due to the specific symmetry of the problem the separation of variables in spherical coordinates is possible in the one-electron Schrodinger equation. Analytical expressions for wave function and energy spectrum are obtained. It is shown that at small values of the stretch angle of spherical sector the problem is reduced to the conical QD problem. The comparison with previously performed works shows good agreement of results. As an application of the obtained results, the quantum transitions in the system are considered.