36 research outputs found
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.
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
Entanglement versus Quantum Discord in Two Coupled Double Quantum Dots
We study the dynamics of quantum correlations of two coupled double quantum
dots containing two excess electrons. The dissipation is included through the
contact with an oscillator bath. We solve the Redfield master equation in order
to determine the dynamics of the quantum discord and the entanglement of
formation. Based on our results, we find that the quantum discord is more
resistant to dissipation than the entanglement of formation for such a system.
We observe that this characteristic is related to whether the oscillator bath
is common to both qubits or not and to the form of the interaction Hamiltonian.
Moreover, our results show that the quantum discord might be finite even for
higher temperatures in the asymptotic limit.Comment: 14 pages, 8 figures (new version is the final version to appear in
NJP
Purity as a witness for initial system-environment correlations in open-system dynamics
We study the dynamics of a two-level atom interacting with a Lorentzian
structured reservoir considering initial system-environment correlations. It is
shown that under strong system-reservoir coupling the dynamics of purity can
determine whether there are initial correlations between system and
environment. Moreover, we investigate the interaction of two two-level atoms
with the same reservoir. In this case, we show that besides determining if
there are initial system-environment correlations, the dynamics of the purity
of the atomic system allows the identification of the distinct correlated
initial states. In addition, the dynamics of quantum and classical correlations
is analyzed.Comment: 6 pages, 3 figure
Exchange effects on electron scattering through a quantum dot embedded in a two-dimensional semiconductor structure
We have developed a theoretical method to study scattering processes of an
incident electron through an N-electron quantum dot (QD) embedded in a
two-dimensional (2D) semiconductor. The generalized Lippmann-Schwinger
equations including the electron-electron exchange interaction in this system
are solved for the continuum electron by using the method of continued
fractions (MCF) combined with 2D partial-wave expansion technique. The method
is applied to a one-electron QD case. Cross-sections are obtained for both the
singlet and triplet couplings between the incident electron and the QD electron
during the scattering. The total elastic cross-sections as well as the
spin-flip scattering cross-sections resulting from the exchange potential are
presented. Furthermore, inelastic scattering processes are also studied using a
multichannel formalism of the MCF.Comment: 11 pages, 4 figure
Artificial molecular quantum rings under magnetic field influence
The ground states of few electrons confined in two vertically coupled quantum
rings in the presence of an external magnetic field are studied systematically
within the current spin-density functional theory. Electron-electron
interactions combined with inter-ring tunneling affects the electronic
structure and the persistent current. For small values of the external magnetic
field, we recover the zero magnetic field molecular quantum ring ground state
configurations. Increasing the magnetic field many angular momentum, spin, and
iso-spin transitions are predicted to occur in the ground state. We show that
these transitions follow certain rules, which are governed by the parity of the
number of electrons, the single particle picture, the Hund's rules and
many-body effects.Comment: accepted for publication in Journal of Applied Physics (in press