59,469 research outputs found
Relativistic Effects of Mixed Vector-Scalar-Pseudoscalar Potentials for Fermions in 1+1 Dimensions
The problem of fermions in the presence of a pseudoscalar plus a mixing of
vector and scalar potentials which have equal or opposite signs is
investigated. We explore all the possible signs of the potentials and discuss
their bound-state solutions for fermions and antifermions. The cases of mixed
vector and scalar P\"{o}schl-Teller-like and pseudoscalar kink-like potentials,
already analyzed in previous works, are obtained as particular cases
Unified Treatment of Mixed Vector-Scalar Screened Coulomb Potentials for Fermions
The problem of a fermion subject to a general mixing of vector and scalar
screened Coulomb potentials in a two-dimensional world is analyzed and
quantization conditions are found.Comment: 7 page
Ambipolar Filamentation of Turbulent Magnetic Fields : A numerical simulation
We present the results of a 2-D, two fluid (ions and neutrals) simulation of
the ambipolar filamentation process, in which a magnetized, weakly ionized
plasma is stirred by turbulence in the ambipolar frequency range. The higher
turbulent velocity of the neutrals in the most ionized regions gives rise to a
non-linear force driving them out of these regions, so that the initial
ionization inhomogeneities are strongly amplified. This effect, the ambipolar
filamentation, causes the ions and the magnetic flux to condense and separate
from the neutrals, resulting in a filamentary structure.Comment: 8 pages, 6 figures, accepted for publication in A&
Distortion of the perfect lattice structure in bilayer graphene
We consider the instability of bilayer graphene with respect to a distorted
configuration in the same spirit as the model introduced by Su, Schrieffer and
Heeger. By computing the total energy of a distorted bilayer, we conclude that
the ground state of the system favors a finite distortion. We explore how the
equilibrium configuration changes with carrier density and an applied potential
difference between the two layers
Stationary states of fermions in a sign potential with a mixed vector-scalar coupling
The scattering of a fermion in the background of a sign potential is
considered with a general mixing of vector and scalar Lorentz structures with
the scalar coupling stronger than or equal to the vector coupling under the
Sturm-Liouville perspective. When the vector coupling and the scalar coupling
have different magnitudes, an isolated solution shows that the fermion under a
strong potential can be trapped in a highly localized region without
manifestation of Klein's paradox. It is also shown that the lonely bound-state
solution disappears asymptotically as one approaches the conditions for the
realization of spin and pseudospin symmetries.Comment: 4 figure
Bilayer graphene: gap tunability and edge properties
Bilayer graphene -- two coupled single graphene layers stacked as in graphite
-- provides the only known semiconductor with a gap that can be tuned
externally through electric field effect. Here we use a tight binding approach
to study how the gap changes with the applied electric field. Within a parallel
plate capacitor model and taking into account screening of the external field,
we describe real back gated and/or chemically doped bilayer devices. We show
that a gap between zero and midinfrared energies can be induced and externally
tuned in these devices, making bilayer graphene very appealing from the point
of view of applications. However, applications to nanotechnology require
careful treatment of the effect of sample boundaries. This being particularly
true in graphene, where the presence of edge states at zero energy -- the Fermi
level of the undoped system -- has been extensively reported. Here we show that
also bilayer graphene supports surface states localized at zigzag edges. The
presence of two layers, however, allows for a new type of edge state which
shows an enhanced penetration into the bulk and gives rise to band crossing
phenomenon inside the gap of the biased bilayer system.Comment: 8 pages, 3 fugures, Proceedings of the International Conference on
Theoretical Physics: Dubna-Nano200
Algebraic solution of a graphene layer in a transverse electric and perpendicular magnetic fields
We present an exact algebraic solution of a single graphene plane in
transverse electric and perpendicular magnetic fields. The method presented
gives both the eigen-values and the eigen-functions of the graphene plane. It
is shown that the eigen-states of the problem can be casted in terms of
coherent states, which appears in a natural way from the formalism.Comment: 11 pages, 5 figures, accepted for publication in Journal of Physics
Condensed Matte
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