146 research outputs found
Microwave-mediated heat transport through a quantum dot
The thermoelectric effect in a quantum dot (QD) attached to two leads in the
presence of microwave fields is studied by using the Keldysh nonequilibrium
Green function technique. When the microwave is applied only on the QD and in
the linear-response regime, the main peaks in the thermoelectric figure of
merit and the thermopower are found to decrease, with the emergence of a set of
photon-induced peaks. Under this condition the microwave field can not generate
heat current or electrical bias voltage. Surprisingly, when the microwave field
is applied only to one (bright) lead and not to the other (dark) lead or the
QD, heat flows mostly from the dark to the bright lead, almost irrespectively
to the direction of the thermal gradient. We attribute this effect to
microwave-induced opening of additional transport channels below the Fermi
energy. The microwave field can change both the magnitude and the sign of the
electrical bias voltage induced by the temperature gradient.Comment: 5 figur
Charge density wave in hidden order state of URuSi
We argue that the hidden order state in URuSi will induce a charge
density wave. The modulation vector of the charge density wave will be twice
that of the hidden order state, . To illustrate how the
charge density wave arises we use a Ginzburg-Landau theory that contains a
coupling of the charge density wave amplitude to the square of the HO order
parameter . This simple analysis allows us to predict the
intensity and temperature dependence of the charge density wave order parameter
in terms of the susceptibilities and coupling constants used in the
Ginzburg-Landau analysis.Comment: 8 pages, 4 figure
Fourier's Law: insight from a simple derivation
The onset of Fourier's law in a one-dimensional quantum system is addressed
via a simple model of weakly coupled quantum systems in contact with thermal
baths at their edges. Using analytical arguments we show that the crossover
from the ballistic (invalid Fourier's law) to diffusive (valid Fourier's law)
regimes is characterized by a thermal length-scale, which is directly related
to the profile of the local temperature. In the same vein, dephasing is shown
to give rise to a classical Fourier's law, similarly to the onset of Ohm's law
in mesoscopic conductors.Comment: 4+ pages, references and discussions adde
Reconstructing Fourier's law from disorder in quantum wires
The theory of open quantum systems is used to study the local temperature and
heat currents in metallic nanowires connected to leads at different
temperatures. We show that for ballistic wires the local temperature is almost
uniform along the wire and Fourier's law is invalid. By gradually increasing
disorder, a uniform temperature gradient ensues inside the wire and the thermal
current linearly relates to this local temperature gradient, in agreement with
Fourier's law. Finally, we demonstrate that while disorder is responsible for
the onset of Fourier's law, the non-equilibrium energy distribution function is
determined solely by the heat baths
Fourier's Law: insight from a simple derivation
The onset of Fourier's law in a one-dimensional quantum system is addressed
via a simple model of weakly coupled quantum systems in contact with thermal
baths at their edges. Using analytical arguments we show that the crossover
from the ballistic (invalid Fourier's law) to diffusive (valid Fourier's law)
regimes is characterized by a thermal length-scale, which is directly related
to the profile of the local temperature. In the same vein, dephasing is shown
to give rise to a classical Fourier's law, similarly to the onset of Ohm's law
in mesoscopic conductors.Comment: 4+ pages, references and discussions adde
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