108 research outputs found
Feasible Nanometric Magnetoresistance Devices
The electrical conductance through a ring is sensitive to the threading
magnetic flux. It contains a component that is periodic with an Aharonov-Bohm
(AB) period equal to the quantum flux. In molecular/atomic loops on the
nanometer scale, encircling very small areas, the AB period involves
unrealistically huge magnetic fields. We show that despite this, moderate
magnetic fields can have a strong impact on the conductance. By controlling the
lifetime of the conduction electron through a pre-selected single state that is
well separated from other states due to the quantum confinement effect, we
demonstrate that magnetic fields comparable to one Tesla can be used to switch
a nanometric AB device. Using atomistic electronic structure calculations, we
show that such effects can be expected for loops composed of monovalent metal
atoms (quantum corals). Our findings suggest that future fabrication of
nanometric magnetoresistance devices is feasible.Comment: 8 pages, 4 figure
Edge Effects in Finite Elongated Graphene Nanoribbons
We analyze the relevance of finite-size effects to the electronic structure
of long graphene nanoribbons using a divide and conquer density functional
approach. We find that for hydrogen terminated graphene nanoribbons most of the
physical features appearing in the density of states of an infinite graphene
nanoribbon are recovered at a length of 40 nm. Nevertheless, even for the
longest systems considered (72 nm long) pronounced edge effects appear in the
vicinity of the Fermi energy. The weight of these edge states scales inversely
with the length of the ribbon and they are expected to become negligible only
at ribbons lengths of the order of micrometers. Our results indicate that
careful consideration of finite-size and edge effects should be applied when
designing new nanoelectronic devices based on graphene nanoribbons. These
conclusions are expected to hold for other one-dimensional systems such as
carbon nanotubes, conducting polymers, and DNA molecules.Comment: 4 pages, 4 figure
- …