9,197 research outputs found
Metallic proximity effect in ballistic graphene with resonant scatterers
We study the effect of resonant scatterers on the local density of states in
a rectangular graphene setup with metallic leads. We find that the density of
states in a vicinity of the Dirac point acquires a strong position dependence
due to both metallic proximity effect and impurity scattering. This effect may
prevent uniform gating of weakly-doped samples. We also demonstrate that even a
single-atom impurity may essentially alter electronic states at low-doping on
distances of the order of the sample size from the impurity.Comment: 9 pages, 2 figure
Ballistic charge transport in chiral-symmetric few-layer graphene
A transfer matrix approach to study ballistic charge transport in few-layer
graphene with chiral-symmetric stacking configurations is developed. We
demonstrate that the chiral symmetry justifies a non-Abelian gauge
transformation at the spectral degeneracy point (zero energy). This
transformation proves the equivalence of zero-energy transport properties of
the multilayer to those of the system of uncoupled monolayers. Similar
transformation can be applied in order to gauge away an arbitrary magnetic
field, weak strain, and hopping disorder in the bulk of the sample. Finally, we
calculate the full-counting statistics at arbitrary energy for different
stacking configurations. The predicted gate-voltage dependence of conductance
and noise can be measured in clean multilayer samples with generic metallic
leads.Comment: 6 pages, 5 figures; EPL published versio
Korshunov instantons out of equilibrium
Zero-dimensional dissipative action possesses non-trivial minima known as
Korshunov instantons. They have been known so far only for imaginary time
representation that is limited to equilibrium systems. In this work we
reconstruct and generalise Korshunov instantons using real-time Keldysh
approach. This allows us to formulate the dissipative action theory for generic
non-equilibrium conditions. Possible applications of the theory to transport in
strongly biased quantum dots are discussed..Comment: 6 pages, 2 figure
Finite-temperature Bell test for quasiparticle entanglement in the Fermi sea
We demonstrate that the Bell test cannot be realized at finite temperatures
in the vast majority of electronic setups proposed previously for quantum
entanglement generation. This fundamental difficulty is shown to originate in a
finite probability of quasiparticle emission from Fermi-sea detectors. In order
to overcome the feedback problem, we suggest a detection strategy, which takes
advantage of a resonant coupling to the quasiparticle drains. Unlike other
proposals, the designed Bell test provides a possibility to determine the
critical temperature for entanglement production in the solid state.Comment: 6 pages, 3 figures, essentially revised and extended versio
Diamagnetism of metallic nanoparticles as the result of strong spin-orbit interaction
The magnetic susceptibility of an ensemble of clean metallic nanoparticles is
shown to change from paramagnetic to diamagnetic one with the onset of
spin-orbit interaction. The effect is quantified on the basis of symmetry
analysis with the help of the random matrix theory. In particular, the magnetic
susceptibility is investigated as the function of symmetry breaking parameter
representing magnetic flux in the crossover from symplectic to unitary and from
orthogonal to unitary ensembles. Corresponding analytical and numerical results
provide a qualitative explanation to the experimental data on diamagnetism of
an ensemble of gold nanorods.Comment: 6 pages, 5 figures; extended versio
Summary and Outlook of the International Workshop on Aging Phenomena in Gaseous Detectors (DESY, Hamburg, October, 2001)
High Energy Physics experiments are currently entering a new era which
requires the operation of gaseous particle detectors at unprecedented high
rates and integrated particle fluxes. Full functionality of such detectors over
the lifetime of an experiment in a harsh radiation environment is of prime
concern to the involved experimenters. New classes of gaseous detectors such as
large-scale straw-type detectors, Micro-pattern Gas Detectors and related
detector types with their own specific aging effects have evolved since the
first workshop on wire chamber aging was held at LBL, Berkeley in 1986. In
light of these developments and as detector aging is a notoriously complex
field, the goal of the workshop was to provide a forum for interested
experimentalists to review the progress in understanding of aging effects and
to exchange recent experiences. A brief summary of the main results and
experiences reported at the 2001 workshop is presented, with the goal of
providing a systematic review of aging effects in state-of-the-art and future
gaseous detectors.Comment: 14 pages, 2 pictures. Presented at the IEEE Nuclear Science Symposium
and Medical Imaging Conference, November 4-10, 2001, San Diego, USA.
Submitted to IEEE Trans. Nucl. Sci (IEEE-TNS
Magnon activation by hot electrons via non-quasiparticle states
We consider the situation when a femtosecond laser pulse creates a hot
electron state in half-metallic ferromagnet (e. g. ferromagnetic semiconductor)
on a picosecond timescale but do not act directly on localized spin system. We
show that the energy and magnetic moment transfer from hot itinerant electrons
to localized spins is facilitated by the so-called non-quasiparticle states,
which are the scattering states of a magnon and spin-majority electron. The
magnon distribution is described by a quantum kinetic equation that we derive
using the Keldysh diagram technique. In a typical ferromagnetic semiconductor
such as EuO magnons remain essentially in non-equilibrium on a scale of the
order of microsecond after the laser pulse.Comment: 8 pages, 2 figure
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