共查询到20条相似文献,搜索用时 406 毫秒
1.
Takaharu Otsuka 《Hyperfine Interactions》1993,78(1-4):19-34
Magnetic dipole and electric quadrupole moments are discussed in terms of the interacting boson model (IBM) and the shell model. From the viewpoint of the IBM, systematic variations of magnetic moments will be discussed by analyzing data of Xe and Ba isotopes. Magnetic and quadrupole moments of various states of Sm and Os isotopes are discussed, pointing out an open problem in the magnetic moments of Os isotopes. The importance of measuring the quadrupole moment of O(6) or -unstable nuclei is emphasized by the example of128Xe. The structure of neutron-rich unstable nuclei will be studied in terms of the shell model, by paying attention to the break-down of the closed shell structure, for instance, the collapse ofN=20 closed shell withZN=20. The magnetic moment of the anomalous ground state of11Be is another topic of this discussion, and it is studied in terms of a new theoretical framework called variational shell model. 相似文献
2.
Kamil Gradkowski Tomasz J. Ochalski Jun Tatebayashi Ganesh Balakrishnan Guillaume Huyet Larry R. Dawson 《Journal of luminescence》2009,129(5):456-460
We present results of room temperature photoreflectance (PR) and photoluminescence (PL) measurements of molecular-beam epitaxy (MBE)-grown GaAsSb/GaAs quantum dot structures: one with an In0.14Ga0.86As capping quantum well and one without it. PL was used to determine the structures’ ground-state transition energies. This result was employed in an 8-band k·p Hamiltonian to achieve a band structure of the structures, which have different electron confinement. The dot emission energies suggest a large amount of As incorporation into the dots, which is due to enhanced adatom mixing at a higher than normal growth temperature of 510 °C. Our calculations indicate a dot composition of 25-50% Sb gives the best fit to experiment. This uncertainty in composition arises due to the fact that different bowing parameters of the ternary alloy could be applied in the calculations. The theoretical analysis accounts well for the main feature in the PR spectra of both samples. 相似文献
3.
The quantum confined Stark effect (QCSE) of the self-assembled InAs/GaAs quantum dots has been investigated theoretically. The ground-state transition energies for quantum dots in the shape of a cube, pyramid or “truncated pyramid” are calculated and analysed. We use a method based on the Green function technique for calculating thestrain in quantum dots and an efficient plane-wave envelope-function technique to determine the ground-state electronic structure of them with different shapes. The symmetry of quantum dots is broken by the effect of strain. So the properties of carriers show different behaviours from the traditional quantum device. Based on these results, we also calculate permanent built-in dipole moments and compare them with recent experimental data. Our results demonstrate that the measured Stark effect in self-assembled InAs/GaAs quantum dot structures can be explained by including linear grading. 相似文献
4.
Shi-Hua Chen 《Pramana》2018,91(6):84
The ratio between the confinement lengths in the xy-plane and the z direction plays an important role in determining the properties of anisotropic quantum dot. Within a variational approach of Pekar type, we investigated theoretically the effects of electric field and temperature on the ground-state binding energies of hydrogenic impurity polarons in KBr anisotropic quantum dot. The obtained results illustrate that the binding energies increase with the electric field strength and temperature but decrease with the position of the impurity when considering different confinement lengths in the xy-plane and the z direction and present the properties of the anisotropic quantum dot. 相似文献
5.
Magnetic dipole and electric quadrupole responses of elliptic quantum dots in magnetic fields 总被引:1,自引:0,他引:1
E. Lipparini Ll. Serra A. Puente 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):409-415
The magnetic dipole (M1) and electric quadupole (E2) responses of two-dimensional quantum dots with an elliptic shape are
theoretically investigated as a function of the dot deformation and applied static magnetic field. Neglecting the electron-electron
interaction we obtain analytical results which indicate the existence of four characteristic modes, with different B-dispersion of their energies and associated strengths. Interaction effects are numerically studied within the time-dependent
local-spin-density and Hartree approximations, assessing the validity of the non-interacting picture.
Received 29 November 2001 Published online 6 June 2002 相似文献
6.
Amand Faessler P. U. Sauer M. M. Stingl 《Zeitschrift für Physik A Hadrons and Nuclei》1968,212(1):1-31
Hartree-Fock (HF) and Hartree-Fock-Bogolyubov (HFB) calculations have been performed for the 1p shell nuclei. Nuclear deformations are assumed to be at most axially symmetric. The HFB transformation is restricted to allow forp-p andn-n pairing only.Volkov's force, a soft-core, two-body interaction of semi-realistic nature, is used which does not produce any single-particle spin-orbit splittings. Coulomb force and the usual correction for centre-of-mass motion are taken into account. The calculations are carried out in a single-particle basis including all states up to principle oscillator quantum numberN=3 (in some cases,N=4). Binding energies, rms radii, density distributions, and quadrupole moments are calculated and found to be in reasonable agreement with experiment. Large Hartree-Fock energy gaps are obtained. They prevent the pairing correlations considered from becoming effective in an HFB approach and from changing the HF ground-state properties appreciably. In non-selfconjugate nuclei, the Pauli principle, rather than the Coulomb interaction, yields large differences between the charge and mass distributions. A theorem on selfconsistent symmetries is proved. The coefficients of the HFB transformation turn out to be real, if time-reversal and angular momentum projection flip are selfconsistent symmetries. 相似文献
7.
With the advent of high-precision frequency combs that can bridge large frequency intervals, new possibilities have opened
up for the laser spectroscopy of atomic transitions. Here, it is shown that laser spectroscopic techniques can also be used
to determine the ground-state g factor of a bound electron. The proposal is based on a double-resonance experiment, where the spin state of a ground-state
electron is constantly being read out by laser excitation to the atomic L shell, while the spin flip transitions are being induced simultaneously by a resonant microwave field, leading to the detection
of the quantum jumps between the ground-state Zeeman sublevels. The magnetic moments of electrons in light hydrogen-like ions
could thus be measured with advanced laser technology. Corresponding theoretical predictions are also presented.
The text was submitted by the authors in English. 相似文献
8.
The ground-state energies of the “bright” and “dark” excitons formed by an electron and a hole localized in a thin spherical shell subjected to a high magnetic field are calculated. This model corresponds to a core/shell quantum dot. The high-field condition implies that the magnetic length is much shorter than the radius of the sphere. It is found that the ground-state energy of the bright exciton exhibits an unusual magnetic-field dependence: E 0 ~ H 2/3. 相似文献
9.
W.-Y. Ruan H.-F. Cheung 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(3):407-411
A coupled quantum dot system has been studied by numerical diagonalization of the Hamiltonian. Discontinuous ground-state
transitions induced by an external magnetic field have been predicted. Series of magic numbers of angular momentum which minimize
the ground-state electron-electron interaction energy have been discovered. Theoretical explanations derived from the first
principles have been formulated.
Received: 13 July 1997 / Accepted: 7 October 1997 相似文献
10.
M. Manninen M. Koskinen S.M. Reimann B. Mottelson 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):381-385
Exact many-body methods as well as current-spin-density functional theory are used to study the magnetism and electron localization
in two-dimensional quantum dots and quasi-one-dimensional quantum rings. Predictions of broken-symmetry solutions within the
density functional model are confirmed by exact configuration interaction (CI) calculations: In a quantum ring the electrons
localize to form an antiferromagnetic chain which can be described with a simple model Hamiltonian. In a quantum dot the magnetic
field localizes the electrons as predicted with the density functional approach.
Received 5 December 2000 相似文献
11.
G. Duchateau E. Cormier R. Gayet 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(2):191-196
A simple theoretical approach based on Coulomb-Volkov states is introduced to predict ionisation of atoms by intense laser
pulses in cases where the effective interaction time does not exceed one or two optical cycles [M. Nisoli et al., Opt. Lett. 22, 522 (1997)]. Under these conditions, the energy distributions of ejected electrons predicted by this non-perturbative approach
are in very good agreement with “exact" results obtained by a full numerical treatment. The agreement is all the better that
the principal quantum number of the initial state is high. For very strong fields, most electrons are ejected at an energy
which is close to the classical kinetic energy that would be transferred to free electrons by the electromagnetic field during
the pulse. The power of the present approach appears when keV. In this region, full numerical treatments become very lengthy and finally do not converge. However, the present Coulomb-Volkov
theory still makes reliable predictions in very short computer times.
Received 19 November 1999 and Received in final form 19 January 2000 相似文献
12.
13.
Governale M 《Physical review letters》2002,89(20):206802
We present results on the effects of spin-orbit coupling on the electronic structure of few-electron interacting quantum dots. The ground-state properties as a function of the number of electrons in the dot N are calculated by means of spin-density functional theory. We find a suppression of Hund's rule due to the competition of the Rashba effect and exchange interaction. Introducing an in-plane Zeeman field leads to a paramagnetic behavior of the dot in a closed-shell configuration and to spin texture in space. 相似文献
14.
Using the shell model wave functions, we have studied quadrupole moments of medium-weight and heavy hypernuclei, and obtained
the shell model values of quadrupole moments of NΛ systems ( N = p and n). With the use of the first-order perturbation
theory, we have also estimated the configuration mixing effects on quadrupole moments of these NΛ hypernuclei. We show that
the hyperon-induced configuration mixing effects are small and the nucleon-induced configuration mixing effects are large
in many cases.
Received: 22 February 2000 / Accepted: 2 August 2000 相似文献
15.
We compute the zero bias conductance of electrons through a single ballistic channel weakly coupled to a side quantum dot with Coulomb interaction. In contrast to the standard setup which is designed to measure the transport through the dot, the channel conductance reveals Coulomb blockade dips rather then peaks due to the Fano-like backscattering. At zero temperature the Kondo effect leads to the formation of broad valleys of small conductance corresponding to an odd number of electrons on the dot. By applying a magnetic field in the dot region we find two dips corresponding to a total suppression in the conductance of spins up and down separated by an energy of the order of the Coulomb interaction. This provides a possibility of a perfect spin filter.Received: 6 November 2003, Published online: 2 April 2004PACS:
72.15.Qm Scattering mechanisms and Kondo effect - 73.23.Ad Ballistic transport - 72.25.-b Spin polarized transport 相似文献
16.
Zongqiang Sheng Zhongzhou Ren 《The European Physical Journal A - Hadrons and Nuclei》2010,46(2):241-247
The ground-state properties of Sn, Te, Xe, and Ba isotopes have been systematically investigated in the framework of the deformed
relativistic mean-field theory with the new parameter set FSUGold. The results show that FSUGold is as successful as NL3 * in reproducing the ground-state binding energies of the nuclei. The calculated two-neutron separation energies, quadrupole
deformations, and root-mean-square (rms) charge radii are in good agreement with the experimental data. The parameter set
FSUGold can successfully describe the shell effect of the neutron magic number N = 82 . Detailed discussions on the binding energies, two-neutron separation energies, quadrupole deformations, rms charge
radii and “binding energies” of the last neutrons are given. 相似文献
17.
S.H. Patil 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(3):341-347
We have developed a simple model potential with a hard core and the correct large-r Coulombic behaviour, to describe the interaction of an electron with a closed shell. One has an exact, analytic ground state
wave function for this potential. This potential is used to develop two-electron perturbed and unperturbed wave functions,
with the correct asymptotic behaviour and cusp conditions. These wave functions allow us to obtain accurate values for the
two-electron energies, polarisabilities, hyperpolarisabilities, and dispersion coefficients of alkaline earth sequences. Many
of these results are the only ones available in the literature.
Received 29 July 1999 and Received in final form 16 November 1999 相似文献
18.
The quantum states of interacting electrons in a quantum dot in a magnetic field are calculated and the effects of corrections to the 2D parabolic model are examined. The quantum states are obtained by a new method which involves three steps: first the electrostatic potential of the device is obtained from a solution of the Poisson equation, next this potential is used together with a combination of variational and Hartree–Fock calculations to obtain an orthogonal basis whose low-lying states are localised in the region of the dot and finally this basis is used to perform an exact diagonalization. Special attention is paid to the effect of motion perpendicular to the ideal 2D plane and the effect of screening of the Coulomb interaction by metallic electrodes close to the dot. Both effects result in a weakened effective interaction and increase the magnetic fields at which ground-state transitions occur. 相似文献
19.
Relativistic analytical expressions are derived for the electric quadrupole moment induced by the hyperfine interaction of the electron with the nucleus of a hydrogen-like atom in the ns1/2 and np1/2 states. The magnetic dipole and electric quadrupole hyperfine interactions are taken into account. The calculations are performed using the generalized virial relationships for the Dirac equation in a central field. The dependences of the electric quadrupole moment on the nuclear charge Z and the principal quantum number n are analyzed. The induced quadrupole moments are compared with the nuclear quadrupole moments. 相似文献
20.
M.V. Moskalets 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(3):523-529
The peculiarities of a low temperature heat transfer through a ballistic quantum dot (a double potential barrier) with interacting
leads due to a long-range Coulomb interaction (in the geometrical capacitance approach) are considered. It is found that the
thermal conductance K shows periodic peaks as a function of the electrostatic potential of a dot at low temperatures. At the peak maximum it is
whereas near the minimum it is . Near the peak maximum the dependence K(T) is essentially nonmonotonic at the temperatures correspondent to the level spacing in the quantum dot.
Received 20 October 1999 and Received in final form 20 January 2000 相似文献