20,084 research outputs found
Radiation induced zero-resistance states: a dressed electronic structure effect
Recent results on magnetoresistance in a two dimensional electron gas under
crossed magnetic and microwave fields show a new class of oscillations,
suggesting a new kind of zero-resistance states. A complete understanding of
the effect is still lacking. We consider the problem from the point of view of
the electronic structure dressed by photons due to a in plane linearly
polarized ac field. The dramatic changes in the dressed electronic structure
lead to a interpretation of the new magnetoresistance oscillations as a
persistent-current like effect, induced by the radiation field.Comment: 5 pages, 5 figures, revtex4, changes in introduction and added
reference
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
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
Columnar Fluctuations as a Source of Non-Fermi-Liquid Behavior in Weak Metallic Magnets
It is shown that columnar fluctuations, in conjunction with weak quenched
disorder, lead to a T^{3/2} temperature dependence of the electrical
resistivity. This is proposed as an explanation of the observed
non-Fermi-liquid behavior in the helimagnet MnSi, with one possible realization
of the columnar fluctuations provided by skyrmion lines that have independently
been proposed to be present in this material.Comment: 4pp, 4 figure
Weak disorder expansion for localization lengths of quasi-1D systems
A perturbative formula for the lowest Lyapunov exponent of an Anderson model on a strip is presented. It is expressed in terms of an energy-dependent doubly stochastic matrix, the size of which is proportional to the strip width. This matrix and the resulting perturbative expression for the Lyapunov exponent are evaluated numerically. Dependence on energy, strip width and disorder strength are thoroughly compared with the results obtained by the standard transfer matrix method. Good agreement is found for all energies in the band of the free operator and this even for quite large values of the disorder strength
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
- …