241 research outputs found
Photoconductance of a one-dimensional quantum dot
The ac-transport properties of a one-dimensional quantum dot with non-Fermi
liquid correlations are investigated. It is found that the linear
photoconductance is drastically influenced by the interaction. Temperature and
voltage dependences of the sideband peaks are treated in detail. Characteristic
Luttinger liquid power laws are founded.Comment: accepted in European Physical Journal
Majorana bound states in hybrid 2D Josephson junctions with ferromagnetic insulators
We consider a Josephson junction consisting of superconductor/ferromagnetic
insulator (S/FI) bilayers as electrodes which proximizes a nearby 2D electron
gas. By starting from a generic Josephson hybrid planar setup we present an
exhaustive analysis of the the interplay between the superconducting and
magnetic proximity effects and the conditions under which the structure
undergoes transitions to a non-trivial topological phase. We address the 2D
bound state problem using a general transfer matrix approach that reduces the
problem to an effective 1D Hamiltonian. This allows for straightforward study
of topological properties in different symmetry classes. As an example we
consider a narrow channel coupled with multiple ferromagnetic superconducting
fingers, and discuss how the Majorana bound states can be spatially controlled
by tuning the superconducting phases. Following our approach we also show the
energy spectrum, the free energy and finally the multiterminal Josephson
current of the setup.Comment: 8 pages; 5 figure
Analogue Casimir Radiation using an Optical Para- metric Oscillator
We establish an explicit analogy between the dynamical Casimir effect and the
photon emission of a thin non-linear crystal pumped inside a cavity. This
allows us to propose a system based on a type-I optical parametric oscillator
(OPO) to simulate a cavity oscillating in vacuum at optical frequencies. The
resulting photon flux is expected to be more easily detectable than with a
mechanical excitation of the mirrors. We conclude by comparing different
theoretical predictions and suggest that our experimental proposal could help
discriminate between them.Comment: 7 pages, 2 figures, epl2 stylefile necessary to compil
A novel experimental approach for the detection of the dynamic Casimir effect
The Casimir effect is a well-known macroscopic consequence of quantum vacuum
fluctuations, but whereas the static effect (Casimir force) has long been
observed experimentally, the dynamic Casimir effect is up to now undetected.
From an experimental viewpoint a possible detection would imply the vibration
of a mirror at gigahertz frequencies. Mechanical motions at such frequencies
turn out to be technically unfeasible. Here we present a different experimental
scheme where mechanical motions are avoided, and the results of laboratory
tests showing that the scheme is practically feasible. We think that at present
this approach gives the only possibility of detecting this phenomenon.Comment: Submitted to the Physical Review Letters. RevTeX. 4 pages, 2 figure
The influence of charge detection on counting statistics
We consider the counting statistics of electron transport through a double
quantum dot with special emphasis on the dephasing induced by a nearby charge
detector. The double dot is embedded in a dissipative enviroment, and the
presence of electrons on the double dot is detected with a nearby quantum point
contact. Charge transport through the double dot is governed by a non-Markovian
generalized master equation. We describe how the cumulants of the current can
be obtained for such problems, and investigate the difference between the
dephasing mechanisms induced by the quantum point contact and the coupling to
the external heat bath. Finally, we consider various open questions of
relevance to future research.Comment: 15 pages, 2 figures, Contribution to 5-th International Conference on
Unsolved Problems on Noise, Lyon, France, June 2-6, 200
Magneto Seebeck effect in REFeAsO (RE=rare earth) compounds: probing the magnon drag scenario
We investigate Seebeck effect in REFeAsO (RE=rare earth)compounds as a
function of temperature and magnetic field up to 30T. The Seebeck curves are
characterized by a broad negative bump around 50K, which is sample dependent
and strongly enhanced by the application of a magnetic field. A model for the
temperature and field dependence of the magnon drag contribution to the Seebeck
effect by antiferromagnetic (AFM) spin fluctuation is developed. It accounts
for the magnitude and scaling properties of such bump feature in our
experimental data. This analysis allows to extract precious information on the
coupling between electrons and AFM spin fluctuations in these parent compound
systems, with implications on the pairing mechanism of the related
superconducting compounds
Spin effects in transport through non-Fermi liquid quantum dots
The current-voltage characteristic of a one dimensional quantum dot connected
via tunnel barriers to interacting leads is calculated in the region of
sequential tunneling. The spin of the electrons is taken into account.
Non-Fermi liquid correlations implying spin-charge separation are assumed to be
present in the dot and in the leads. It is found that the energetic distance of
the peaks in the linear conductance shows a spin-induced parity effect at zero
temperature T. The temperature dependence of the positions of the peaks depends
on the non-Fermi liquid nature of the system. For non-symmetric tunnel barriers
negative differential conductances are predicted, which are related to the
participation in the transport of collective states in the quantum dot with
larger spins. Without spin-charge separation the negative differential
conductances do not occur. Taking into account spin relaxation destroys the
spin-induced conductance features. The possibility of observing in experiment
the predicted effects are briefly discussed.Comment: 15 pages, 16 figures, accepted for publication on Physical Review
Shot noise of a quantum dot with non-Fermi liquid correlations
The shot noise of a one-dimensional wire interrupted by two barriers shows
interesting features related to the interplay between Coulomb blockade effects,
Luttinger correlations and discrete excitations. At small bias the Fano factor
reaches the lowest attainable value, 1/2, irrespective of the ratio of the two
junction resistances. At larger voltages this asymmetry is power-law
renormalized by the interaction strength. We discuss how the measurement of
current and these features of the noise allow to extract the Luttinger liquid
parameter.Comment: 4 pages, 3 figures,to be published in Phys. Rev. B. For high
resolution image of Fig.1 see http://server1.fisica.unige.it/~braggio/doc.ht
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