289 research outputs found
Thermoelectric effects in Kondo correlated quantum dots
In this Letter we study thermoelectric effects in ultra small quantum dots.
We study the behaviour of the thermopower, Peltier coefficient and thermal
conductance both in the sequencial tunneling regime and in the regime where
Kondo correlations develope. Both cases of linear response and non-equilibrium
induced by strong temperature gradients are considered. The thermopower is a
very sensitive tool to detect Kondo correlations. It changes sign both as a
function of temperature and temperature gradient. We also discuss violations of
the Wiedemann-Franz law.Comment: 7 pages; 5 figure
Thermal rectification effect of an interacting quantum dot
We investigate nonlinear thermal transport properties of a single interacting
quantum dot with two energy levels tunnel-coupled to two electrodes using
nonequilibrium Green function method and Hartree-Fock decoupling approximation.
In the case of asymmetric tunnel-couplings to two electrodes, for example, when
the upper level of the quantum dot is open for transport, whereas the lower
level is blocked, our calculations predict a strong asymmetry for the heat
(energy) current, which shows that, the quantum dot system may act as a thermal
rectifier in this specific situation.Comment: 5 pages, 5 figure
Experimental Evidence for Coulomb Charging Effects in an Open Quantum Dot at Zero Magnetic Field
We have measured the low-temperature transport properties of an open quantum
dot formed in a clean one-dimensional channel. For the first time, at zero
magnetic field, continuous and periodic oscillations superimposed upon
ballistic conductance steps are observed when the conductance through the dot
exceeds . We ascribe the observed conductance oscillations to
evidence for Coulomb charging effects in an open dot. This is supported by the
evolution of the oscillating features for as a function of both
temperature and barrier transparency. Our results strongly suggest that at zero
magnetic field, current theoretical and experimental understanding of Coulomb
charging effects overlooks charging in the presence of fully transmitted 1D
channels.Comment: To appear in Phys. Rev. Lett. 81 (Oct 19 issue
Disorder, pseudospins, and backscattering in carbon nanotubes
We address the effects of disorder on the conducting properties of metal and
semiconducting carbon nanotubes. Experimentally, the mean free path is found to
be much larger in metallic tubes than in doped semiconducting tubes. We show
that this result can be understood theoretically if the disorder potential is
long-ranged. The effects of a pseudospin index that describes the internal
sublattice structure of the states lead to a suppression of scattering in
metallic tubes, but not in semiconducting tubes. This conclusion is supported
by tight-binding calculations.Comment: four page
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