32,051 research outputs found
Inner and outer edge states in graphene rings: A numerical investigation
We numerically investigate quantum rings in graphene and find that their
electronic properties may be strongly influenced by the geometry, the edge
symmetries and the structure of the corners. Energy spectra are calculated for
different geometries (triangular, hexagonal and rhombus-shaped graphene rings)
and edge terminations (zigzag, armchair, as well as the disordered edge of a
round geometry). The states localized at the inner edges of the graphene rings
describe different evolution as a function of magnetic field when compared to
those localized at the outer edges. We show that these different evolutions are
the reason for the formation of sub-bands of edge states energy levels,
separated by gaps (anticrossings). It is evident from mapping the charge
densities that the anticrossings occur due to the coupling between inner and
outer edge states.Comment: 8 pages, 7 figures. Figures in low resolution due to size
requirements - higher quality figures on reques
A non-perturbative study of matter field propagators in Euclidean Yang-Mills theory in linear covariant, Curci-Ferrari and maximal Abelian gauges
In this work, we study the propagators of matter fields within the framework
of the Refined Gribov-Zwanziger theory, which takes into account the effects of
the Gribov copies in the gauge-fixing quantization procedure of Yang-Mills
theory. In full analogy with the pure gluon sector of the Refined
Gribov-Zwanziger action, a non-local long-range term in the inverse of the
Faddeev-Popov operator is added in the matter sector. Making use of the recent
BRST invariant formulation of the Gribov-Zwanziger framework achieved in [Capri
et al 2016], the propagators of scalar and quark fields in the adjoint and
fundamental representations of the gauge group are worked out explicitly in the
linear covariant, Curci-Ferrari and maximal Abelian gauges. Whenever lattice
data are available, our results exhibit good qualitative agreement.Comment: 27 pages, no figures; V2, minor modifications, to appear in EPJ
Third edge for a graphene nanoribbon: A tight-binding model calculation
The electronic and transport properties of an extended linear defect embedded
in a zigzag nanoribbon of realistic width are studied, within a tight binding
model approach. Our results suggest that such defect profoundly modify the
properties of the nanoribbon, introducing new conductance quantization values
and modifying the conductance quantization thresholds. The linear defect along
the nanoribbon behaves as an effective third edge of the system, which shows a
metallic behavior, giving rise to new conduction pathways that could be used in
nanoscale circuitry as a quantum wire.Comment: 6 pages, 6 figures. Two new figures and a few references adde
Resonant tunneling through protected quantum dots at phosphorene edges
We theoretically investigate phosphorene zigzag nanorribons as a platform for
constriction engineering. In the presence of a constriction at the upper edge,
quantum confinement of edge protected states reveals resonant tunnelling
Breit-Wigner transmission peaks, if the upper edge is uncoupled to the lower
edge. Coupling between edges in thin constrictions gives rise to Fano-like and
anti-resonances in the transmission spectrum of the system.Comment: 8 pages,7 figure
Vortices in the presence of a nonmagnetic atom impurity in 2D XY ferromagnets
Using a model of nonmagnetic impurity potential, we have examined the
behavior of planar vortex solutions in the classical two-dimensional XY
ferromagnets in the presence of a spin vacancy localized out of the vortex
core. Our results show that a spinless atom impurity gives rise to an effective
potential that repels the vortex structure.Comment: 6 pages, 2 figures, RevTex
Non-perturbative treatment of the linear covariant gauges by taking into account the Gribov copies
In this paper, a proposal for the restriction of the Euclidean functional
integral to a region free of infinitesimal Gribov copies in linear covariant
gauges is discussed. An effective action, akin to the Gribov-Zwanziger action
of the Landau gauge, is obtained which implements the aforementioned
restriction. Although originally non-local, this action can be cast in local
form by introducing auxiliary fields. As in the case of the Landau gauge,
dimension two condensates are generated at the quantum level, giving rise to a
refinement of the action which is employed to obtain the tree-level gluon
propagator in linear covariant gauges. A comparison of our results with those
available from numerical lattice simulations is also provided.Comment: 21 pages, no figures, version to appear in EPJ
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