590 research outputs found
Polarized currents and spatial separation of Kondo state: NRG study of spin-orbital effect in a double QD
A double quantum dot device, connected to two channels that only see each
other through interdot Coulomb repulsion, is analyzed using the numerical
renormalization group technique. By using a two-impurity Anderson model, and
parameter values obtained from experiment [S. Amasha {\it et al.}, Phys. Rev.
Lett. {\bf 110}, 046604 (2013)], it is shown that, by applying a moderate
magnetic field, and adjusting the gate potential of each quantum dot, opposing
spin polarizations are created in each channel. Furthermore, through a well
defined change in the gate potentials, the polarizations can be reversed. This
polarization effect is clearly associated to a spin-orbital Kondo state having
a Kondo peak that originates from spatially separated parts of the device. This
fact opens the exciting possibility of experimentally probing the internal
structure of an SU(2) Kondo state.Comment: 4+ pages; 4 figures; supplemental material (1 page, 2 figures
Transport properties of strongly correlated electrons in quantum dots using a simple circuit model
Numerical calculations are shown to reproduce the main results of recent
experiments involving nonlocal spin control in nanostructures (N. J. Craig et
al., Science 304, 565 (2004)). In particular, the splitting of the
zero-bias-peak discovered experimentally is clearly observed in our studies. To
understand these results, a simple "circuit model" is introduced and shown to
provide a good qualitative description of the experiments. The main idea is
that the splitting originates in a Fano anti-resonance, which is caused by
having one quantum dot side-connected in relation to the current's path. This
scenario provides an explanation of Craig et al.'s results that is alternative
to the RKKY proposal, which is here also addressed.Comment: 5 pages, 5 figure
Effect of topology on the transport properties of two interacting dots
The transport properties of a system of two interacting dots, one of them
directly connected to the leads constituting a side-coupled configuration
(SCD), are studied in the weak and strong tunnel-coupling limits. The
conductance behavior of the SCD structure has new and richer physics than the
better studied system of two dots aligned with the leads (ACD). In the weak
coupling regime and in the case of one electron per dot, the ACD configuration
gives rise to two mostly independent Kondo states. In the SCD topology, the
inserted dot is in a Kondo state while the side-connected one presents Coulomb
blockade properties. Moreover, the dot spins change their behavior, from an
antiferromagnetic coupling to a ferromagnetic correlation, as a consequence of
the interaction with the conduction electrons. The system is governed by the
Kondo effect related to the dot that is embedded into the leads. The role of
the side-connected dot is to introduce, when at resonance, a new path for the
electrons to go through giving rise to the interferences responsible for the
suppression of the conductance. These results depend on the values of the
intra-dot Coulomb interactions. In the case where the many-body interaction is
restricted to the side-connected dot, its Kondo correlation is responsible for
the scattering of the conduction electrons giving rise to the conductance
suppression
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