355 research outputs found
Thermally-activated non-local amplification in quantum energy transport
We study energy-transport efficiency in light-harvesting planar and 3D
complexes of two-level atomic quantum systems, embedded in a common thermal
blackbody radiation. We show that the collective non-local dissipation induced
by the thermal bath plays a fundamental role in energy transport. It gives rise
to a dramatic enhancement of the energy-transport efficiency, which may largely
overcome . This effect, which improves the understanding of transport
phenomena in experimentally relevant complexes, suggests a particularly
promising mechanism for quantum energy management.Comment: 7 pages, 4 figures. New version in which the RP line of Figure 1 has
been amended with the correct parameter
Near-field refrigeration and tunable heat exchange through four-wave mixing
We modify and extend a recently proposed four-wave mixing scheme [Opt.
Express 25 (19),23164 (2017)] for achieving near-field thermal upconversion and
energy transfer, to demonstrate efficient thermal refrigeration at low
intensities W/m over a wide range of gap sizes (from tens to
hundreds of nanometers) and operational temperatures (from tens to hundreds of
Kelvins). We further exploit the scheme to achieve magnitude and directional
tunability of near-field heat exchange between bodies held at different
temperatures
Casimir-Lifshitz force out of thermal equilibrium between dielectric gratings
We calculate the Casimir-Lifshitz pressure in a system consisting of two
different 1D dielectric lamellar gratings having two different temperatures and
immersed in an environment having a third temperature. The calculation of the
pressure is based on the knowledge of the scattering operators, deduced using
the Fourier Modal Method. The behavior of the pressure is characterized in
detail as a function of the three temperatures of the system as well as the
geometrical parameters of the two gratings. We show that the interplay between
non-equilibrium effects and geometrical periodicity offers a rich scenario for
the manipulation of the force. In particular, we find regimes where the force
can be strongly reduced for large ranges of temperatures. Moreover, a repulsive
pressure can be obtained, whose features can be tuned by controlling the
degrees of freedom of the system. Remarkably, the transition distance between
attraction and repulsion can be decreased with respect to the case of two
slabs, implying an experimental interest for the observation of repulsion.Comment: 13 pages, 11 figures, accepted on Phys. Rev.
Distributed thermal tasks on many-body systems through a single quantum machine
We propose a configuration of a single three-level quantum emitter embedded
in a non-equilibrium steady electromagnetic environment, able to stabilize and
control the local temperatures of a target system it interacts with, consisting
of a collection of coupled two-level systems. The temperatures are induced by
dissipative processes only, without the need of further external couplings for
each qubit. Moreover, by acting on a set of easily tunable geometric
parameters, we demonstrate the possibility to manipulate and tune each qubit
temperature independently over a remarkably broad range of values. These
findings address one standard problem in quantum-scale thermodynamics,
providing a way to induce a desired distribution of temperature among
interacting qubits and to protect it from external noise sources.Comment: 6 pages, 5 figure
Radiative heat transfer between metallic gratings using adaptive spatial resolution
We calculate the radiative heat transfer between two identical metallic
one-dimensional lamellar gratings. To this aim we present and exploit a
modification to the widely-used Fourier modal method, known as adaptive spatial
resolution, based on a stretch of the coordinate associated to the periodicity
of the grating. We first show that this technique dramatically improves the
rate of convergence when calculating the heat flux, allowing to explore smaller
separations. We then present a study of heat flux as a function of the grating
height, highlighting a remarkable amplification of the exchanged energy,
ascribed to the appearance of spoof-plasmon modes, whose behavior is also
spectrally investigated. Differently from previous works, our method allows us
to explore a range of grating heights extending over several orders of
magnitude. By comparing our results to recent studies we find a consistent
quantitative disagreement with some previously obtained results going up to
50\%. In some cases, this disagreement is explained in terms of an incorrect
connection between the reflection operators of the two gratings.Comment: 10 pages, 6 figures. Some typos corrected with respect to the
previous versio
Surface-mode-assisted amplification of radiative heat transfer between nanoparticles
We show that the radiative heat flux between two nanoparticles can be
significantly amplified when they are placed in proximity of a planar substrate
supporting a surface resonance. The amplification factor goes beyond two orders
of magnitude in the case of dielectric nanoparticles, whereas it is lower in
the case of metallic nanoparticles. We analyze how this effect depends on the
frequency and on the particles-surface distance, by clearly identifying the
signature of the surface mode producing the amplification. Finally, we show how
the presence of a graphene sheet on top of the substrate can modify the effect,
by making an amplification of two orders of magnitude possible also in the case
of metallic nanoparticles. This long range amplification effect should play an
important role in the thermal relaxation dynamics of nanoparticle networks.Comment: 10 pages, 8 figure
Lifetimes of atoms trapped in an optical lattice in proximity of a surface
We study the lifetime of an atom trapped in an optical vertical lattice in
proximity of a massive surface using a complex scaling approach. We analyze how
the presence of the surface modifies the known lifetimes of Wannier-Stark
states associated to Landau-Zener tunnelling. We also investigate how the
existence of a hypothetical short-distance deviation from Newton's
gravitational law could affect these lifetimes. Our study is relevant in order
to discuss the feasibility of any atomic- interferometry experiment performed
near a surface. Finally, the difficulties encountered in applying the
complex-scaling approach to the atom-surface Casimir-Polder interaction are
addressed.Comment: 10 pages, 8 figure
Graphene-based amplification and tuning of near-field radiative heat transfer between dissimilar polar materials
The radiative heat transfer between two dielectrics can be strongly enhanced
in the near field in the presence of surface phonon-polariton resonances.
Nevertheless, the spectral mismatch between the surface modes supported by two
dissimilar materials is responsible for a dramatic reduction of the radiative
heat flux they exchange. In the present paper we study how the presence of a
graphene sheet, deposited on the material supporting the surface wave of lowest
frequency, allows to widely tune the radiative heat transfer, producing an
amplification factor going up to one order of magnitude. By analyzing the
Landauer energy transmission coefficients we demonstrate that this
amplification results from the interplay between the delocalized plasmon
supported by graphene and the surface polaritons of the two dielectrics. We
finally show that the effect we highlight is robust with respect to the
frequency mismatch, paving the way to an active tuning and amplification of
near-field radiative heat transfer in different configurations.Comment: 8 pages, 8 figure
- …