Electron-acoustic-phonon scattering and electron relaxation in two-coupled quantum rings

Electron relaxation, induced by acoustic phonons, is studied for coupled quantum rings in the presence of external fields, both electric and magnetic. We address the problem of a single electron in vertically coupled GaAs quantum rings. Electron-phonon interaction is accounted for both deformation potential and piezoelectric field coupling mechanisms. Depending on the external fields, the ring radii and the separation between the rings, we show that the two different couplings have different weights and importance. Significant oscillations are found in the scattering rates from electron excited states to the ground state, as a function of either the geometry of the system or the external fields.Comment: 17 pages, 8 figures, to appear in Journal of Applied Physic

Inelastic Coulomb scattering rate of a multisubband Q1D electron gas

In this work, the Coulomb scattering lifetimes of electrons in two coupled quantum wires have been studied by calculating the quasiparticle self-energy within a multisubband model of quasi-one-dimensional (Q1D) electron system. We consider two strongly coupled quantum wires with two occupied subbands. The intrasubband and intersubband inelastic scattering rates are caculated for electrons in different subbands. Contributions of the intrasubband, intersubband plasmon excitations, as well as the quasiparticle excitations are investigated. Our results shows that the plasmon exictations of the first subband are the most important scattering mechanism for electrons in both subbands.Comment: 9 pages, REVTEX, 2 figure

Hamiltonian of a many-electron system with single-electron and electron-pair states in a two-dimensional periodic potential

Based on the metastable electron-pair energy band in a two-dimensional (2D) periodic potential obtained previously by Hai and Castelano [J. Phys.: Condens. Matter 26, 115502 (2014)], we present in this work a Hamiltonian of many electrons consisting of single electrons and electron pairs in the 2D system. The electron-pair states are metastable of energies higher than those of the single-electron states at low electron density. We assume two different scenarios for the single-electron band. When it is considered as the lowest conduction band of a crystal, we compare the obtained Hamiltonian with the phenomenological model Hamiltonian of a boson-fermion mixture proposed by Friedberg and Lee [Phys. Rev. B 40, 6745 (1989)]. Single-electron-electron-pair and electron-pair-electron-pair interaction terms appear in our Hamiltonian and the interaction potentials can be determined from the electron-electron Coulomb interactions. When we consider the single-electron band as the highest valence band of a crystal, we show that holes in this valence band are important for stabilization of the electron-pair states in the system

Anomalous Rashba spin-orbit interaction in InAs/GaSb quantum wells

We investigate theoretically the Rashba spin-orbit interaction in InAs/GaSb quantum wells(QWs). We find that the Rashba spin-splitting (RSS) depends sensitively on the thickness of the InAs layer. The RSS exhibits nonlinear behavior for narrow InAs/GaSb QWs and the oscillating feature for wide InAs/GaSb QWs. The nonlinear and oscillating behaviors arise from the weakened and enhanced interband coupling. The RSS also show asymmetric features respect to the direction of the external electric field.Comment: 3 pages, 4 figures. Appl. Phys. Lett. (in press

Control of the persistent currents in two interacting quantum rings through the Coulomb interaction and inter-ring tunneling

The persistent current in two vertically coupled quantum rings containing few electrons is studied. We find that the Coulomb interaction between the rings in the absence of tunneling affects the persistent current in each ring and the ground state configurations. Quantum tunneling between the rings alters significantly the ground state and the persistent current in the system.Comment: accepted for publication in Phys. Rev.

Carrier relaxation due to electron-electron interaction in coupled double quantum well structures

We calculate the electron-electron interaction induced energy-dependent inelastic carrier relaxation rate in doped semiconductor coupled double quantum well nanostructures within the two subband approximation at zero temperature. In particular, we calculate, using many-body theory, the imaginary part of the full self-energy matrix by expanding in the dynamically RPA screened Coulomb interaction, obtaining the intrasubband and intersubband electron relaxation rates in the ground and excited subbands as a function of electron energy. We separate out the single particle and the collective excitation contributions, and comment on the effects of structural asymmetry in the quantum well on the relaxation rate. Effects of dynamical screening and Fermi statistics are automatically included in our many body formalism rather than being incorporated in an ad-hoc manner as one must do in the Boltzman theory.Comment: 26 pages, 5 figure

Levinson's Theorem for the Klein-Gordon Equation in Two Dimensions

The two-dimensional Levinson theorem for the Klein-Gordon equation with a cylindrically symmetric potential $V(r)$ is established. It is shown that $N_{m}\pi=\pi (n_{m}^{+}-n_{m}^{-})= [\delta_{m}(M)+\beta_{1}]-[\delta_{m}(-M)+\beta_{2}]$, where $N_{m}$ denotes the difference between the number of bound states of the particle $n_{m}^{+}$ and the ones of antiparticle $n_{m}^{-}$ with a fixed angular momentum $m$, and the $\delta_{m}$ is named phase shifts. The constants $\beta_{1}$ and $\beta_{2}$ are introduced to symbol the critical cases where the half bound states occur at $E=\pm M$.Comment: Revtex file 14 pages, submitted to Phys. Rev.

Artificial molecular quantum rings: Spin density functional theory calculations

The ground states of artificial molecules made of two vertically coupled quantum rings are studied within the spin density functional theory for systems containing up to 13 electrons. Quantum tunneling effects on the electronic structure of the coupled rings are analyzed. For small ring radius, our results recover those of coupled quantum dots. For intermediate and large ring radius, new phases are found showing the formation of new diatomic artificial ring molecules. Our results also show that the tunneling induced phase transitions in the coupled rings occur at much smaller tunneling energy as compared to those for coupled quantum dot systems.Comment: 10 pages, 6 figure