119 research outputs found
Breakdown of detailed balance for thermal radiation by synthetic fields
In recent times the possibility of non-reciprocity in heat transfer between
two bodies has been extensively studied. In particular the role of strong
magnetic fields has been investigated. A much simpler approach with
considerable flexibility would be to consider heat transfer in synthetic
electric and magnetic fields which are easily applied. We demonstrate the
breakdown of detailed balance for the heat transfer function , i.e. the spectrum of heat transfer between two objects due to the
presence of synthetic electric and magnetic fields. The spectral measurements
carry lot more physical information and were the reason for the quantum theory
of radiation. We demonstrate explicitly the synthetic field induced
non-reciprocity in the heat transfer transmission function between two graphene
flakes and for the Casimir coupling between two objects. Unlike many other
cases of heat transfer, the latter case has interesting features of the strong
coupling. Further the presence of synthetic fields affects the mean occupation
numbers of two membranes and propose this system for the experimental
verification of the breakdown of detailed balance
Enhancement of synthetic magnetic field induced nonreciprocity via bound states in continuum in dissipatively coupled systems
The nonreciprocal propagation of light typically requires use of materials
like ferrites or magneto-optical media with a strong magnetic bias or methods
based on material nonlinearities which require use of strong electromagnetic
fields. A simpler possibility to produce nonreciprocity is to use
spatio-temporal modulations to produce magnetic fields in synthetic dimensions.
In this paper we show that dissipatively coupled systems can lead to
considerable enhancement of nonreciprocity in synthetic fields. The enhancement
comes about from the existence of nearly nondecaying mode -bound state in
continuum (BIC) in dissipatively coupled systems. The dissipative coupling
occurs in a wide class of systems coupled via transmission lines, waveguides,
or nano fibers. The systems could be optical resonators or microscopic qubits.
Remarkably we find that for specific choice of the modulation amplitudes, the
transmission say in forward direction is completely extinguished whereas in the
backward direction it becomes maximum. The synthetic fields produce
transmission resonances which show significant line narrowing which owe their
origin to existence of BIC's in dissipative systems
Nonreciprocal heat flux via synthetic fields in linear quantum systems
We study the heat transfer between N coupled quantum resonators with applied
synthetic electric and magnetic fields realized by changing the resonators
parameters by external drivings. To this end we develop two general methods,
based on the quantum optical master equation and on the Langevin equation for
coupled oscillators where all quantum oscillators can have their own heat
baths. The synthetic electric and magnetic fields are generated by a dynamical
modulation of the oscillator resonance with a given phase. Using Floquet theory
we solve the dynamical equations with both methods which allow us to determine
the heat flux spectra and the transferred power. With apply these methods to
study the specific case of a linear tight-binding chain of four quantum coupled
resonators. We find that in that case, in addition to a non-reciprocal heat
flux spectrum already predicted in previous investigations, the synthetic
fields induce here non-reciprocity in the total heat flux hence realizing a net
heat flux rectification
The plasmonic eigenvalue problem
A plasmon of a bounded domain is a non-trivial
bounded harmonic function on which is
continuous at and whose exterior and interior normal
derivatives at have a constant ratio. We call this ratio a
plasmonic eigenvalue of . Plasmons arise in the description of
electromagnetic waves hitting a metallic particle . We investigate
these eigenvalues and prove that they form a sequence of numbers converging to
one. Also, we prove regularity of plasmons, derive a variational
characterization, and prove a second order perturbation formula. The problem
can be reformulated in terms of Dirichlet-Neumann operators, and as a side
result we derive a formula for the shape derivative of these operators.Comment: 22 pages; replacement 8-March-14: minor corrections; to appear in
Review in Mathematical Physic
Near-field heat transfer between a nanoparticle and a rough surface
In this work we focus on the surface roughness correction to the near-field
radiative heat transfer between a nanoparticle and a material with a rough
surface utilizing a direct perturbation theory up to second order in the
surface profile. We discuss the different distance regimes for the local
density of states above the rough material and the heat flux analytically and
numerically. We show that the heat transfer rate is larger than that
corresponding to a flat surface at short distances. At larger distances it can
become smaller due to surface polariton scattering by the rough surface. For
distances much smaller than the correlation length of the surface profile, we
show that the results converge to a proximity approximation, whereas in the
opposite limit the rough surface can be replaced by an equivalent surface
layer
Anomalous photon thermal Hall effect
We predict an anomalous thermal Hall effect (ATHE) mediated by photons in
networks of Weyl semi-metals. Contrary to the photon thermal Hall effect in
magneto-optical systems which requires the application of an external magnetic
field the ATHE in a Weyl semi-metals network is an intrinsic property of these
systems. Since the Weyl semi-metals can exhibit a strong nonreciprocal response
in the infrared over a broad spectral range the magnitude of thermal Hall flux
in these systems can be relatively large compared to the primary flux. This
ATHE paves the way for a directional control of heat flux by localy tuning the
magnitude of temperature field without changing the direction of temperature
gradient
Statistical properties of spontaneous emission near a rough surface
We study the lifetime of the excited state of an atom or molecule near a
plane surface with a given random surface roughness. In particular, we discuss
the impact of the scattering of surface modes within the rough surface. Our
study is completed by considering the lateral correlation length of the decay
rate and the variance discussing its relation to the C0 correlation
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