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1.
Effects of Electric Field on Electronic States in a GaAs/GaAlAs Quantum Dot with Different Confinements 下载免费PDF全文
Binding energies of shallow hydrogenic impurity in a GaAs/GaAlAs quantum dot with spherical confinement, parabolic confinement and rectangular confinement are calculated as a function of dot radius in the influence of electric field. The binding energy is calculated following a variational procedure within the effective mass approximation along with the spatial depended dielectric function. A finite confining potential well with depth is determined by the discontinuity of the band gap in the quantum dot and the cladding. It is found that the contribution of spatially dependent screening effects are small for a donor impurity and it is concluded that the rectangulax confinement is better than the parabolic and spherical confinements. These results are compared with the existing literature. 相似文献
2.
Wenfang Xie 《Physica B: Condensed Matter》2008,403(17):2828-2831
The energy levels of an off-center hydrogenic donor confined by a spherical Gaussian potential have been calculated as a function of the potential radius for different donor position by exact diagonalization method. The results have clearly demonstrated the so-called quantum size effect. The binding energy is dependent on the dot radius R, the impurity ion distance D, and the confining potential depth V0. 相似文献
3.
In this paper, we have studied electronic properties of a two-electron quantum dot using Tietz confining potential in the presence of an external magnetic field. In this regard, we have applied diagonalization procedure of Hamilonian matrix. We have calculated singlet-triplet ground state transitions as a function of the magnetic field. The obtained results show that the dot size of the Tietz potential has an important role in the ground state transition. The singlet-triplet transition of the ground state shifts towards lower magnetic field when the quantum size increases. Our results yield much less transitions than that of previous results [R.G. Nazmitdinov, N.S. Simonovic, and M.J. Rost, Phys.Rev. B 65(2002) 155307]. 相似文献
4.
In this paper, we have studied electronic properties of a two-electron quantum dot using Tietz confining potential in the presence of an external magnetic field. In this regard, we have applied diagonalization procedure of Hamilonian matrix. We have calculated singlet-triplet ground state transitions as a function of the magnetic field. The obtained results show that the dot size of the Tietz potential has an important role in the ground state transition. The singlet-triplet transition of the ground state shifts towards lower magnetic field when the quantum size increases. Our results yield much less transitions than that of previous results [R.G. Nazmitdinov, N.S. Simonovic, and M.J. Rost, Phys. Rev. B 65 (2002) 155307]. 相似文献
5.
采用线性组合算符和幺正变换方法,研究非对称量子点中强耦合磁极化子的激发态性质。导出强耦合磁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的跃迁谱线频率随量子点的横向和纵向有效受限长度、磁场的回旋频率和电子-声子耦合强度的变化关系。数值计算结果表明:第一内部激发态能量、激发能量和跃迁谱线频率随磁场的回旋频率和电子-声子耦合强度的增加而增大.随量子点的横向和纵向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。 相似文献
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7.
In this paper, an exciton trapped by a Gaussian confining potential quantum
dot has been investigated. Calculations are made by using the method of
numerical diagonalization of Hamiltonian in the effective-mass
approximation. The dependences of binding energies of the ground state and
the first excited state on the size of the confining potential and the
strength of the magnetic field are analysed explicitly. 相似文献
8.
Using an exact analytical method, we obtain the ground state and the excited states wave functions as well as the corresponding eigenvalues of a spherical quantum dot in the presence of a confining potential which is a combination of linear, Coulomb and quadratic terms. Next, we investigate the quantum dot energy as the potential coefficients are changed. Our study reveals that considering such a confining potential leads to results which are in good agreement with experimental results. 相似文献
9.
The motion of a few electrons in a three-dimensional harmonic oscillator potential under the influence of a homogeneous magnetic field of arbitrary direction is studied. The ground state of the Fermi system is obtained by minimizing the total energy with regard to the confining frequencies. From this a dependence of the equilibrium shape on the electron number, the magnetic field parameters and the slab thickness is found. 相似文献
10.
XIE Wen-Fang 《理论物理通讯》2006,46(6):1101-1104
We study the energy spectra of a two-dimensional two-electron quantum dot
(QD) with Pöschl-Teller confining potential under the influence of
perpendicular homogeneous magnetic field. Calculations are made by using the method of numerical diagonalization of Hamiltonian matrix within the
effective-mass approximation. A ground-state behavior (spin singlet-triplet
transitions) as a function of the strength of a magnetic field is
found. We find that the dot radius R of a Pöschl-Teller potential is
important for the ground-state transition and the feature of ground-state for a Pöschl-Teller QD and a parabolic QD is similar when R is larger. The larger the well depth, the higher the magnetic field for the
singlet-triplet transition of the ground-state of two interacting electrons in a Pöschl-Teller QD. 相似文献
11.
Sr.Gerardin JayamK. Navaneethakrishnan 《Solid State Communications》2003,126(12):681-685
The binding energies of a hydrogenic donor in a GaAs spherical quantum dot in the Ga1−xAlxAs matrix are presented assuming parabolic confinement. Effects of hydrostatic pressure and electric field are discussed on the results obtained using a variational method. Effects of the spatial variation of the dielectric screening and the effective mass mismatch are also investigated. Our results show that (i) the ionization energy decreases with dot size, with the screening function giving uniformly larger values for dots which are less than about 25 nm, (ii) the hydrostatic pressure increases the donor ionization energy such that the variation is larger for a smaller dot, and (iii) the ionization energy decreases in an electric field. All the calculations have been carried out with finite barriers and good agreement is obtained with the results available in the literature in limiting cases. 相似文献
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13.
M.G. BarseghyanAlireza Hakimyfard A.A. KirakosyanM.E. Mora-Ramos C.A. Duque 《Superlattices and Microstructures》2012,51(1):119-127
We consider the effects of electric and magnetic fields as well as of hydrostatic pressure on the donor binding energy in InAs Pöschl-Teller quantum rings. The ground state energy and the electron wave function are calculated within the effective mass and parabolic band approximations, using the variational method. The binding energy dependencies on the electric field strength and the hydrostatic pressure are reported for different values of quantum ring size and shape, the parameters of the Pöschl-Teller confining potential, and the magnetic field induction. The results show that the binding energy is an increasing or decreasing function of the electric field, depending on the chosen parameters of the confining potential. Also, we have observed that the binding energy is an increasing/decreasing function of hydrostatic pressure/magnetic field induction. Likewise, the impurity binding energy behaves as an increasing/decreasing function of the inner/outer radii of the quantum ring nanostructure. 相似文献
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15.
T. Ouchterlony I.V. Zozoulenko C.-K. Wang K.-F. Berggren C. Gould A.S. Sachrajda 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(2):361-370
We study the conductance of a square quantum dot, modeling the potential with a self-consistent Thomas-Fermi approximation.
The resulting potential is characterized by level statistics indicative of mixed chaotic and regular electron dynamics within
the dot in spite of the regular geometry of the gates defining the dot. We calculate numerically, for the case of a quantum
dot with soft confinement, the weak localization (WL) correction. We demonstrate that this confining potential may generate
either Lorentzian or linear lineshapes depending on the number of modes in the leads. Finally, we present experimental WL
data for a lithographically square dot and compare the results with numerical calculations. We analyze the experimental results
and numerical simulations in terms of semiclassical and random matrix theory (RMT) predictions and discuss their limitations
as far as real experimental structures are concerned. Our results indicate that direct application of the above predictions
to distinguish between chaotic and regular dynamics in a particular cavity can not always lead to reliable conclusions as
the shape and magnitude of the WL correction can be strongly sensitive to the geometry-specific, non-universal features of
the system.
Received 13 May 1998 相似文献
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17.
R.S. Daries Bella 《Solid State Communications》2004,130(11):773-776
The ground state and a few excited state energies of a hydrogenic donor in a spherical quantum dot (GaAs in a GaAlAs matrix) are computed. While the 1s and the 2s-state energies behave normally for dots of all radii, the 2p0 and 2p± states are unbound for most of the radii of interest. It is predicted that a semiconductor quantum dot with a hydrogenic donor will exhibit photoconductivity for a low threshold wavelength ∼12 μm. The spin-orbit coupling gives a contribution of the order of 10−5 meV for both 2p0 and 2p± states. 相似文献
18.
We explore the dynamics of harmonically confined single electron quantum dots as a function of dot size under periodically fluctuating confinement potential. The system of interest is a 2-D system in the presence of a perpendicular magnetic field. We show that for given strengths of the magnetic field and effective mass, a periodic variation in the strength of the confinement potential could invite interesting features in the dynamics of the system. Also, the pattern of time evolution of eigenstates of the unperturbed system reveals significant size-dependence. The fluctuation in the confinement potential from its initial value is found to modulate the dynamical aspects in a prominent way. The presence of cubic anharmonicity in the confining field brings in new features in the dot dynamics. 相似文献
19.
We study the eigenstates in quantum dots in which electrons are confined by the application of an inhomogeneous perpendicular magnetic field, focusing on the effect that the specific details of the shape of confining field has on determining these states. In contrast to the edge state picture established in studies on circular dots, we find that dots with more irregular geometries show a more complicated behavior in the interior of the dot. In particular, we find that certain states show indications of having their amplitude enhanced along particular classical periodic orbits in the interior, a phenomenon known as ‘scarring’. 相似文献
20.
XIE Wen-Fang 《理论物理通讯》2008,49(2):507-510
The properties of the low-lying states of a negative donor center trapped by
a spherical quantum dot, which is subjected to a parabolic potential
confinement, are investigated in the absence of magnetic field. The
calculations have been performed by means of the exact diagonalization of
the Hamiltonian matrix within the effective-mass approximation. We find that there is only one bound state the D- center in a spherical parabolic quantum dot in the absence of magnetic field. The binding energy of the ground state is obtained as a function of the dot size. Moreover, the critical confined potential radius value at which the negative donor center changes from unbound to bound is obtained. 相似文献