12,070 research outputs found
Topological superconductivity in lead nanowires
Superconductors with an odd number of bands crossing the Fermi energy have
topologically protected Andreev states at interfaces, including Majorana states
in one dimensional geometries. Superconductivity, a low number of 1D channels,
large spin orbit coupling, and a sizeable Zeeman energy, are present in lead
nanowires produced by nanoindentation of a Pb tip on a Pb substrate, in
magnetic fields higher than the Pb bulk critical field. A number of such
devices have been analyzed. In some of them, the dependence of the critical
current on magnetic field, and the Multiple Andreev Reflections observed at
finite voltages, are compatible with the existence of topological
superconductivity
Electron Fabry-Perot interferometer with two entangled magnetic impurities
We consider a one-dimensional (1D) wire along which single conduction
electrons can propagate in the presence of two spin-1/2 magnetic impurities.
The electron may be scattered by each impurity via a contact-exchange
interaction and thus a spin-flip generally occurs at each scattering event.
Adopting a quantum waveguide theory approach, we derive the stationary states
of the system at all orders in the electron-impurity exchange coupling
constant. This allows us to investigate electron transmission for arbitrary
initial states of the two impurity spins. We show that for suitable electron
wave vectors, the triplet and singlet maximally entangled spin states of the
impurities can respectively largely inhibit the electron transport or make the
wire completely transparent for any electron spin state. In the latter case, a
resonance condition can always be found, representing an anomalous behaviour
compared to typical decoherence induced by magnetic impurities. We provide an
explanation for these phenomena in terms of the Hamiltonian symmetries.
Finally, a scheme to generate maximally entangled spin states of the two
impurities via electron scattering is proposed.Comment: 19 page
Effect of Static Disorder in an Electron Fabry-Perot Interferometer with Two Quantum Scattering Centers
In a recent paper -- F. Ciccarello \emph{et al.}, New J. Phys. \textbf{8},
214 (2006) -- we have demonstrated that the electron transmission properties of
a one-dimensional (1D) wire with two identical embedded spin-1/2 impurities can
be significantly affected by entanglement between the spins of the scattering
centers. Such effect is of particular interest in the control of transmission
of quantum information in nanostructures and can be used as a detection scheme
of maximally entangled states of two localized spins. In this letter, we relax
the constraint that the two magnetic impurities are equal and investigate how
the main results presented in the above paper are affected by a static disorder
in the exchange coupling constants of the impurities. Good robustness against
deviation from impurity symmetry is found for both the entanglement dependent
transmission and the maximally entangled states generation scheme.Comment: 4 pages, 5 figure
Consumer behavior in the intentions to change between electricity suppliers in Portugal: A push-pull-mooring framework
The liberalization process of the Portuguese electricity market, which started in the 1990s, is integrated in the strategic action enacted by the European Union (EU). With the introduction of competition in the electricity sector, it became essential for electricity providers to identify which factors determine consumers' choice and switching between electricity suppliers. This study intends to apply the push-pull-mooring migration theory to consumers in the electricity market to understand the switching behavior between suppliers. The results showed that push and mooring dimensions have a significant impact on consumer switching intention. In general, low satisfaction and higher value-billing of the other services can push consumers away from their current electricity supplier. Furthermore, these results suggest that the moderating effects such as the switching costs, the previous experience in this market as well as the social influence play important roles in the relationship between some components of the push effects (commitment, satisfaction, and value-billing other services) and the intention to change. Therefore, this study helps both market players and public policy makers designing strategies and incentives aligned with consumer behavior, considering both economic and psychological factors and their combined effect in their switching intention.info:eu-repo/semantics/acceptedVersio
All-optical trapping and acceleration of heavy particles
A scheme for fast, compact, and controllable acceleration of heavy particles
in vacuum is proposed, in which two counterpropagating lasers with variable
frequencies drive a beat-wave structure with variable phase velocity, thus
allowing for trapping and acceleration of heavy particles, such as ions or
muons. Fine control over the energy distribution and the total charge of the
beam is obtained via tuning of the frequency variation. The acceleration scheme
is described with a one-dimensional theory, providing the general conditions
for trapping and scaling laws for the relevant features of the particle beam.
Two-dimensional, electromagnetic particle-in-cell simulations confirm the
validity and the robustness of the physical mechanism.Comment: 10 pages, 3 figures, to appear in New Journal of Physic
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