4,727 research outputs found
Faraday Rotation, Band Splitting, and One-Way Propagation of Plasmon Waves on a Nanoparticle Chain
We calculate the dispersion relations of plasmonic waves propagating along a
chain of semiconducting or metallic nanoparticles in the presence of both a
static magnetic field and a liquid crystalline host. The dispersion
relations are obtained using the quasistatic approximation and a dipole-dipole
approximation to treat the interaction between surface plasmons on different
nanoparticles. For a plasmons propagating along a particle chain in a nematic
liquid crystalline host with both and the director parallel to the
chain, we find a small, but finite, Faraday rotation angle. For
perpendicular to the chain, but director still parallel to the chain, the field
couples the longitudinal and one of the two transverse plasmonic branches. This
coupling is shown to split the two branches at the zero field crossing by an
amount proportional to . In a cholesteric liquid crystal host and an
applied magnetic field parallel to the chain, the dispersion relations for
left- and right-moving waves are found to be different. For some frequencies,
the plasmonic wave propagates only in one of the two directions.Comment: 6 pages, 4 figures. arXiv admin note: substantial text overlap with
arXiv:1502.0496
Model of the Longitudinal Spin Seebeck Coefficient of InSb in a Magnetic Field
We develop a simple theory for the longitudinal spin Seebeck effect in
n-doped InSb in an external magnetic field. We consider spin- electrons in
the conduction band of InSb with a temperature gradient parallel to the applied
magnetic field. In the absence of spin-orbit interactions, a Boltzmann equation
approach leads to a spin current parallel to the field and proportional to the
temperature gradient. The calculated longitudinal spin Seebeck coefficients
oscillates as a function of magnetic field B; the peak positions are
approximately periodic in 1/B. The oscillations arise when the Fermi energy
crosses the bottom of a Landau band.Comment: 7 pages, 6 figure
Theory of plasmonic waves on a chain of metallic nanoparticles in a liquid crystalline host
A chain of metallic particles, of sufficiently small diameter and spacing,
allows linearly polarized plasmonic waves to propagate along the chain. In this
paper, we describes how these waves are altered when the liquid crystal host is
a nematic or a cholesteric liquid crystal (NLC or CLC) with or without an
applied magnetic field. We find that, in general, the liquid crystal host,
either NLC or CLC, alters the dispersion relations of the transverse () and
longitudinal () waves significantly from the dispersion relations for an
isotropic host. We show that by altering the director axis of the liquid
crystal relative to the long axis of the metallic chain, that the branch
can be split into two non-degenerate linearly polarized branches (NLC host) or
two non-degenerate elliptically polarized branches (CLC host). When an external
magnetic field is applied parallel to both the long axis of the metallic
particles and the director of the CLC host, we find that the dispersion
relations are odd in an exchange in sign for for the non-degenerate
elliptically polarized branches. That is, the application of an external
magnetic field leads to the realization of a one-way waveguide.Comment: 9 Pages, 3 Figures. arXiv admin note: text overlap with
arXiv:1210.150
Graphene with adatoms: tuning the magnetic moment with an applied voltage
We show that, in graphene with a small concentration of adatoms, the total
magnetic moment can be switched on and off by varying the Fermi energy
, either by applying a gate voltage or by suitable chemical doping. Our
calculation is carried out using a simple tight-binding model described
previously, combined with a mean-field treatment of the electron-electron
interaction on the adatom. The values of at which the moment is turned on
or off are controlled by the strength of the hopping between the graphene sheet
and the adatom, the on-site energy of the adatom, and the strength of the
electron-electron correlation energy U. Our result is in qualitatively
consistent with recent experiments by Nair {\it et al.} [Nat.\ Commun.\ {\bf
4}, 2010 (2013)].Comment: 4 Pages, 1 Figur
Tight-Binding Model for Adatoms on Graphene: Analytical Density of States, Spectral Function, and Induced Magnetic Moment
In the limit of low adatom concentration, we obtain exact analytic
expressions for the local and total density of states (LDOS, TDOS) for a
tight-binding model of adatoms on graphene. The model is not limited to
nearest-neighbor hopping but can include hopping between carbon atoms at any
separation. We also find an analytical expression for the spectral function
of an electron of Bloch vector and energy E on the
graphene lattice, to first order in the adatom concentration. We treat the
electron-electron interaction by including a Hubbard term on the adatom, which
we solve within a mean-field approximation. For finite Hubbard , we find the
spin-polarized LDOS, TDOS, and spectral function self-consistently. For any
choice of parameters of the tight-binding model within mean field theory, we
find a critical value of above which a moment develops on the adatom. For
most choices of parameters, we find a substantial charge transfer from the
adatom to the graphene host.Comment: 11 Pages, 6 figures, 1 tabl
Microscopes and computers combined for analysis of chromosomes
Scanning machine CHLOE, developed for photographic use, is combined with a digital computer to obtain quantitative and statistically significant data on chromosome shapes, distribution, density, and pairing. CHLOE permits data acquisition about a chromosome complement to be obtained two times faster than by manual pairing
Al Jazeera and the DoD: The Need for Greater Engagement
A review of the recently published Capstone Concept for Joint Operations (CCJO) highlights a complex
security environment marked by an ever-changing and easily accessible global information network.
Because of this expanding phenomenon, military actions and operations will be conducted under increased
media scrutiny and will require greater transparency especially for the international audience. Additionally,
U.S. military operations within the Middle East will be widely scrutinized by a global Muslim audience, who
has become more distrustful and critical of U.S. policies and military strategy. As such, this necessitates
greater engagement with international news networks by the U.S. Department of Defense (DoD) and its
military services. In particular, the Al Jazeera Media Network represents one of the fastest growing and
most influential news networks among the myriad media who dominate the global information environment.
This research highlights the need for the DoD and the Joint Services to examine current communication
strategies with the Al Jazeera Media Network and incorporate the findings into its senior leader
engagement plan and its leader development strategies for public affairs and communication specialists
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