733 research outputs found
Competitive 0 and {\pi} states in S/F multilayers: multimode approach
We have investigated the critical temperature behavior in periodic
superconductor/ ferromagnet (S/F) multilayers as a function of the
ferromagnetic layer thickness and the interface transparency. The
critical temperature exhibits a damped oscillatory behavior in these
systems due to an exchange field in the ferromagnetic material. In this work we
have performed calculations using the self-consistent multimode approach,
which is considered to be exact solving method. Using this approach we have
derived the conditions of 0 or state realization in periodic S/F
multilayers. Moreover, we have presented the comparison between the single-mode
and multimode approaches and established the limits of applicability of the
single-mode approximation, frequently used by experimentalists
Analysis of airplane boarding via space-time geometry and random matrix theory
We show that airplane boarding can be asymptotically modeled by 2-dimensional
Lorentzian geometry. Boarding time is given by the maximal proper time among
curves in the model. Discrepancies between the model and simulation results are
closely related to random matrix theory. We then show how such models can be
used to explain why some commonly practiced airline boarding policies are
ineffective and even detrimental.Comment: 4 page
Antiferromagnetic resonances in superconductor-ferromagnet multilayers
In this work, we study magnetization dynamics in superconductor-ferromagnet
(S-F) thin-film multilayer. Theoretical considerations supported by the
broad-band ferromagnetic resonance spectroscopy reveal development of acoustic
and optic resonance modes in S-F multilayers at significantly higher
frequencies in comparison to the Kittel mode of individual F-layers. These
modes are formed due to antiferromagnetic-like interaction between F-layers via
shared circulating superconducting currents in S-layers. The gap between
resonance modes is determined by the thickness and superconducting penetration
depth in S-layers. Overall, rich spectrum of S-F multilayers and its tunability
opens wide prospects for application of these multialyers in magnonics as well
as in various superconducting hybrid systems.Comment: 5 pages, 4 figures, 34 reference
Double Fe-impurity charge state in the topological insulator BiSe
The influence of individual impurities of Fe on the electronic properties of
topological insulator BiSe is studied by Scanning Tunneling Microscopy.
The microscope tip is used in order to remotely charge/discharge Fe impurities.
The charging process is shown to depend on the impurity location in the
crystallographic unit cell, on the presence of other Fe impurities in the close
vicinity, as well as on the overall doping level of the crystal. We present a
qualitative explanation of the observed phenomena in terms of tip-induced local
band bending. Our observations evidence that the specific impurity neighborhood
and the position of the Fermi energy with respect to the Dirac point and bulk
bands have both to be taken into account when considering the electron
scattering on the disorder in topological insulators.Comment: 10 pages, accepted for publication in Applied Physics Letters, minor
bugs were correcte
Tunable Resonant Raman Scattering from Singly Resonant Single Wall Carbon Nanotubes
We perform tunable resonant Raman scattering on 17 semiconducting and 7
metallic singly resonant single wall carbon nanotubes. The measured scattering
cross-section as a function laser energy provides information about a tube's
electronic structure, the lifetime of intermediate states involved in the
scattering process and also energies of zone center optical phonons. Recording
the scattered Raman signal as a function of tube location in the microscope
focal plane allows us to construct two-dimensional spatial maps of singly
resonant tubes. We also describe a spectral nanoscale artifact we have coined
the "nano-slit effect"
Tight inequalities for nonclassicality of measurement statistics
In quantum optics, measurement statistics -- for example, photocounting
statistics -- are considered nonclassical if they cannot be reproduced with
statistical mixtures of classical radiation fields. We have formulated a
necessary and sufficient condition for such nonclassicality. This condition is
given by a set of inequalities that tightly bound the convex set of
probabilities associated with classical electromagnetic radiation. Analytical
forms for full sets and subsets of these inequalities are obtained for
important cases of realistic photocounting measurements and unbalanced homodyne
detection. As an example, we consider photocounting statistics of
phase-squeezed coherent states. Contrary to a common intuition, the analysis
developed here reveals distinct nonclassical properties of these statistics
that can be experimentally corroborated with minimal resources.Comment: 12 pages, 4 figure
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