124 research outputs found
Full counting statistics for SU(N) impurity Anderson model
We analyze the full counting statistics of a multiorbital Kondo effect in a
quantum dotwith the SU(N) symmetry in the framework of the renormalized
perturbation theory. The current probability distribution function is
calculated for an arbitrary dot-site Coulomb repulsion in the particle-hole
symmetric case. The resulting cumulant up to the leading nonlinear term of
applied bias voltages indicates two types of electron transfer, respectively
carrying charge and , with different -dependences. The cross
correlation between different orbital currents shows exponential enhancement
with respect to , which directly addresses formation of the orbital-singlet
state.Comment: 1 figure, 1 table, 5 page
Full counting statistics for orbital-degenerate impurity Anderson model with Hund's rule exchange coupling
We study non-equilibrium current fluctuations through a quantum dot, which
includes a ferromagnetic Hund's rule coupling , in the low-energy Fermi
liquid regime using the renormalized perturbation theory. The resulting
cumulant for the current distribution in the particle-hole symmetric case,
shows that spin-triplet and spin-singlet pairs of quasiparticles are formed in
the current due to the Hund's rule coupling and these pairs enhance the current
fluctuations. In the fully screened higher-spin Kondo limit, the Fano factor
takes a value determined by the orbital degeneracy .
We also investigate crossover between the small and large limits in the
two-orbital case M=2, using the numerical renormalization group approach.Comment: 5 pages, 3 figure
Electron transport through Aharonov-Bohm interferometer with laterally coupled double quantum dots
We theoretically investigate electron transport through an Aharonov-Bohm
interferometer containing laterally coupled double quantum dots. We introduce
the indirect coupling parameter , which characterizes the strength of
the coupling via the reservoirs between two quantum dots.
indicates the strongest coupling, where only a single mode contributes to the
transport in the system. Two conduction modes exist in a system where
. The interference effects such as the Fano resonance and the
Aharonov-Bohm oscillation are suppressed as the absolute value of the parameter
decreases from 1. The linear conductance does not depend on the flux
when since it corresponds to independent coupling of the dots to the
reservoir modes.Comment: 15 pages, 13 figure
Phonon-mediated spin dynamics in a two-electron double quantum dot under a phonon temperature gradient
We have theoretically studied phonon-mediated spin-flip processes of
electrons in a GaAs double quantum dot (DQD) holding two spins, under a phonon
temperature gradient over the DQD. Transition rates of inter-dot
phonon-assisted tunnel processes and intra-dot spin-flip processes involving
spin triplet states are formalized by the electron-phonon interaction
accompanied with the spin-orbit interaction. The calculations of the spin-flip
rates and the occupation probabilities of the spin-states in the two-electron
DQD with respect to the phonon temperature difference between the dots are
quantitatively consistent with our previous experiment. This theoretical study
on the temperature gradient effect onto spins in coupled QDs would be essential
for understanding spin-related thermodynamic physics
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