68 research outputs found
Non-Markovian dynamics in the theory of full counting statistics
We consider the theoretical description of real-time counting of electrons
tunneling through a Coulomb-blockade quantum dot using a detector with finite
bandwidth. By tracing out the quantum dot we find that the dynamics of the
detector effectively is non-Markovian. We calculate the cumulant generating
function corresponding to the resulting non-Markovian rate equation and find
that the measured current cumulants behave significantly differently compared
to those of a Markovian transport process. Our findings provide a novel
interpretation of noise suppression found in a number of systems.Comment: 4 pages, 1 figure, Contribution to ICNF 2007, Tokyo, Japan,
September, 200
Transport of fractional Hall quasiparticles through an antidot
Current statistics of an antidot in the fractional quantum Hall regime is
studied for Laughlin's series. The chiral Luttinger liquid picture of edge
states with a renormalized interaction exponent is adopted. Several
peculiar features are found in the sequential tunneling regime. On one side,
current displays negative differential conductance and double-peak structures
when . On the other side, universal sub-poissonian transport regimes are
identified through an analysis of higher current moments. A comparison between
Fano factor and skewness is proposed in order to clearly distinguish the charge
of the carriers, regardless of possible non-universal interaction
renormalizations. Super-poissonian statistics is obtained in the shot limit for
, and plasmonic effects due to the finite-size antidot are tracked.Comment: accepted for publication in Phys. Rev. B, references adde
Counting statistics of transport through Coulomb blockade nanostructures: High-order cumulants and non-Markovian effects
Recent experimental progress has made it possible to detect in real-time
single electrons tunneling through Coulomb blockade nanostructures, thereby
allowing for precise measurements of the statistical distribution of the number
of transferred charges, the so-called full counting statistics. These
experimental advances call for a solid theoretical platform for equally
accurate calculations of distribution functions and their cumulants. Here we
develop a general framework for calculating zero-frequency current cumulants of
arbitrary orders for transport through nanostructures with strong Coulomb
interactions. Our recursive method can treat systems with many states as well
as non-Markovian dynamics. We illustrate our approach with three examples of
current experimental relevance: bunching transport through a two-level quantum
dot, transport through a nano-electromechanical system with dynamical
Franck-Condon blockade, and transport through coherently coupled quantum dots
embedded in a dissipative environment. We discuss properties of high-order
cumulants as well as possible subtleties associated with non-Markovian
dynamics.Comment: 27 pages, 8 figures, 1 table, final version as published in Phys.
Rev.
Current enhancement through a time dependent constriction in fractional topological insulators
We analyze the backscattering current induced by a time dependent
constriction as a tool to probe fractional topological insulators. We
demonstrate an enhancement of the total current for a fractional topological
insulator induced by the dominant tunneling excitation, contrary to the
decreasing present in the integer case for not too strong interactions. This
feature allows to unambiguously identify fractional quasiparticles.
Furthermore, the dominant tunneling processes, which may involve one or two
quasiparticles depending on the interactions, can be clearly determined.Comment: 6 pages, 3 figure
3+1D Massless Weyl spinors from bosonic scalar-tensor duality
We consider the fermionization of a bosonic free theory characterized by the
3+1D scalar - tensor duality. This duality can be interpreted as the
dimensional reduction, via a planar boundary, of the 4+1D topological BF
theory. In this model, adopting the Sommerfield tomographic representation of
quantized bosonic fields, we explicitly build a fermionic operator and its
associated Klein factor such that it satisfies the correct anticommutation
relations. Interestingly, we demonstrate that this operator satisfies the
massless Dirac equation and that it can be identified with a 3+1D Weyl spinor.
Finally, as an explicit example, we write the integrated charge density in
terms of the tomographic transformed bosonic degrees of freedom
Holography in flat spacetime: 4D theories and electromagnetic duality on the border
We consider a free topological model in 5D euclidean flat spacetime, built
from two rank-2 tensor fields. Despite the fact that the bulk of the model does
not have any particular physical interpretation, on its 4D planar edge
nontrivial gauge field theories are recovered, whose features are entirely
determined by the gauge and discrete symmetries of the bulk. In particular no
4D dynamics can be obtained without imposing a Time Reversal invariance in the
bulk. Remarkably, one of the two possible edge models selected by the Time
Reversal symmetries displays a true electromagnetic duality, which relates
strong and weak coupling regimes. Moreover this same model, when considered
on-shell, coincides with the Maxwell theory, which therefore can be thought of
as a 4D boundary theory of a seemingly harmless 5D topological model.Comment: 21 pages, plain LaTeX, no figures. Version to appear on JHE
Analytic DC thermo-electric conductivities in holography with massive gravitons
We provide an analytical derivation of the thermo-electric transport
coefficients of the simplest momentum-dissipating model in gauge/gravity where
the lack of momentum conservation is realized by means of explicit graviton
mass in the bulk. We rely on the procedure recently described by Donos and
Gauntlett in the context of Q-lattices and holographic models where momentum
dissipation is realized through non-trivial scalars. The analytical approach
confirms the results found previously by means of numerical computations.Comment: 9 pages, no figures, minor comments added, version to appear on PR
Thermoelectric single-photon detection through superconducting tunnel junctions
Bipolar thermoelectricity in tunnel junctions between superconductors of
different energy gap has been recently predicted and experimentally
demonstrated. This effect showed thermovoltages up to V at
milliKelvin temperatures. Thus, superconducting tunnel junctions can be
exploited to realize a passive single-photon thermoelectric detector
operating in the broadband range 15 GHz - 50 PHz. In particular, this detector
is expected to show a signal-to-noise ratio of about 15 down to GHz
and a operating window of more than 4 decades. Therefore, the might find
applications in quantum computing, telecommunications, optoelectronics,
spectroscopy and astro-particle physics.Comment: 7 pages, 3 figure
Bipolar thermoelectrical SQUIPT (BTSQUIPT)
We theoretically study the quasiparticle current behaviour of a
thermally-biased bipolar thermoelectrical superconducting quantum interference
proximity transistor, formed by a normal metal wire embedded in a
superconducting ring and tunnel-coupled to a superconducting probe. In this
configuration, the superconducting gap of the wire can be modified through an
applied magnetic flux. We analyse the thermoelectric response as a function of
magnetic flux, at fixed temperatures, in the case of a device made of the same
superconductor. We demonstrate magnetically controllable, bipolar
thermoelectric behaviour and discuss optimal working conditions by looking at
the thermoelectric power and other figures of merit of the device.Comment: 6 pages, 4 figure
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