Case Of Single Electron Research Articles

Electronic structure of rectangular HgTe quantum dots

We theoretically investigate the single- and few-electron ground-states properties of HgTe topological insulator quantum dots with rectangular hard-wall confining potential using configuration interaction method. For the case of single electron, the edge states is robust against the deformation from a square quantum dot to a rectangular ones, in contrast to the bulk states, the energy gap of the QDs increased due to the coupling of the opposite edge states; for the case of few electrons, the electrons first fill the edge states in the bulk band gap and the addition energy exhibit universal even-odd oscillation due to the shape-independent two-fold degeneracy of the edge states. The size of this edge shell can be controlled by tuning the dot size, shape or the bulk band gap via lateral or vertical electric gating respectively of the HgTe quantum dot.

Broken scaling laws of the transition probabilities from jj to LS coupling transitions

Accurate electromagnetic transition rates between the ground electronic configurations are important in diagnostic studies of planetary nebulae. Based on a “quasi-complete basis” set, we present large-scale multi-configuration Dirac–Fock calculations of the forbidden transition rates within the ground electronic configuration along the nitrogen-like isoelectronic sequence. The broken scaling laws of the transition probabilities from jj to LS coupling transitions are elucidated and found to be extensions of the well-known scaling laws discussed in the single electron case. The equivalent oscillator strength is very large for ions in high-Z regions and should play a crucial role in the cooling mechanism in astrophysics. • We did an MCDF calculation of forbidden transition rates between the lowest 5 states of N-like ions. • The broken scaling laws of the transition rates from jj to LS coupling transition are elucidated. • These scaling laws are an extension of the scaling laws discussed in the single electron picture. • The equivalent oscillator strength of forbidden transitions will be very large for high-Z ions. • These transitions of high-Z ions should be important cooling mechanisms of the relevant plasmas.

EFFECTS OF ON-CENTER IMPURITY ON ENERGY LEVELS OF LOW-LYING STATES IN CONCENTRIC DOUBLE QUANTUM RINGS

In this paper, the electronic eigenstates and energy spectra of single and two-interacting electrons confined in a concentric double quantum rings with a perpendicular magnetic field in the presence of on-center donor and acceptor impurities are calculated using the exact diagonalization method. For a single electron case, the binding energy of on-center donor and acceptor impurities are also calculated. The effects of centrifugal, confinement and diamagnetic potentials on the binding energy are investigated. It is found that the binding energy decreases by increasing the centrifugal or confinement potential. Also, it is shown that the binding energy increases by increasing the magnetic field. The effects of on-center impurity on the energy spectrum and angular momentum transition of the lowest states are investigated for the both single and two-interacting electrons. It is found that the on-center donor impurity increases the fractional Aharonov-Bohm oscillation period while the acceptor impurity acts inversely and decreases the fractional AharonovBohm oscillation period.

?Spectral characteristics of nonlinear Compton backscattering of an ultra-intense laser pulse by relativistic electrons

The nonlinear Compton backscattered radiation of an ultra-intense laser pulse by counterpropagating relativistic electrons was numerically investigated. The spectral characteristics of high-order harmonics were analyzed for a single electron case. In the case of an electron beam, the harmonic spectrum was investigated based on beam parameters. With a 32-MeV electron beam and a 10-Hz, 5×10-W/cm laser pulse, 10 ∼ 10 photons/s in a 1% bandwidth could be generated in the range of 10 ∼ 80 keV.

Wigner Function for Identical Particles

In this work the Wigner function approach to quantum transport developed for the single electron case is extended to a more complicated system for n indistingushable particles. In particular we study how the Monte Carlo tecnique and the Wigner paths method can be applyed to a single particle Wigner function defined for a system of n interacting particles. The numerical results are obtained for the case of a system of two particles under different conditions: two noninteracting fermions, two noninteracting bosons, two non interacting distinguishable particles and two interacting fermions.

Polaronic behavior in single- and many-electron Holstein model: A new perturbation approach

A new perturbation approach is developed for single- and many-electron Holstein model in one-, two-, and three-dimension. The results show that this approach has a good agreement with the Migdal theory in the adiabatic regime when the coupling is moderate (λ < 1), but with the Lang-Firsov theory in the antiadiabatic regime ( ω/W≫ 1). In the intermediate region, our approach can describe the transition from a large-polaron Fermi-liquid to the small-polaron, and this transition may be discontinuous in adiabatic regime, which means a phase transition appears in many-electron system. In single-electron case, we eliminate the abrupt transition using the degenerate perturbation theory, and the calculated ground state energy and effective mass are successfully compared with those of previous authors. Besides, the method has the advantage of requiring little computational effort.

Dynamical properties of the one-dimensional Holstein model

The spectral weight functions and the optical conductivity of the Holstein model are studied on a one-dimensional six-site lattice with periodic boundary conditions for three different electron concentrations: a single electron, two electrons of opposite spins, and half filling. A density matrix approach is used to obtain an optimal phonon basis and to truncate the phonon Hilbert space without significant loss of accuracy. This approach allows us to calculate spectral functions for electrons dressed locally by the optimal phonons as well as for bare electrons. We obtain evidence for a smooth crossover from quasi-free electrons to an heavy itinerant small polaron (single-electron case) or bipolaron (two-electron case) as the electron-phonon coupling strength increases. At half filling we observe a crossover from a quasi-free-electron ground state to a quasi-degenerate Peierls charge-density-wave ground state for a finite electron-phonon coupling. This crossover is marked by an abrupt drop of the Drude weight which is vanishingly small in the Peierls phase.