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

Fermionic symmetry-protected topological state in strained graphene

The low-energy physics of graphene is described by relativistic Dirac fermions with spin and valley degrees of freedom. Mechanical strain can be used to create a pseudo magnetic field pointing to opposite directions in the two valleys. We study interacting electrons in graphene exposed to both an external real magnetic field and a strain-induced pseudo magnetic field. For a certain ratio between these two fields, it is proposed that a fermionic symmetry-protected topological state can be realized. The state is characterized in detail using model wave functions, Chern-Simons field theory, and numerical calculations. Our paper suggests that graphene with artificial gauge fields may host a rich set of topological states.Comment: 8 pages, 4 figure