454 research outputs found
A cosmological model for corrugated graphene sheets
Defects play a key role in the electronic structure of graphene layers flat
or curved. Topological defects in which an hexagon is replaced by an n-sided
polygon generate long range interactions that make them different from
vacancies or other potential defects. In this work we review previous models
for topological defects in graphene. A formalism is proposed to study the
electronic and transport properties of graphene sheets with corrugations as the
one recently synthesized. The formalism is based on coupling the Dirac equation
that models the low energy electronic excitations of clean flat graphene
samples to a curved space. A cosmic string analogy allows to treat an arbitrary
number of topological defects located at arbitrary positions on the graphene
plane. The usual defects that will always be present in any graphene sample as
pentagon-heptagon pairs and Stone-Wales defects are studied as an example. The
local density of states around the defects acquires characteristic modulations
that could be observed in scanning tunnel and transmission electron microscopy.Comment: Proceedings of the Graphene Conference, MPI PKS Dresden, September
200
A condensed matter realization of the axial magnetic effect
The axial magnetic effect, i.e., the generation of an energy current parallel
to an axial magnetic field coupling with opposite signs to left- and
right-handed fermions is a non-dissipative transport phenomenon intimately
related to the gravitational contribution to the axial anomaly. An axial
magnetic field emerges naturally in condensed matter in the so called Weyl
semi-metals. We present a measurable implementation of the axial magnetic
effect. We show that the edge states of a Weyl semimetal at finite temperature
possess a temperature dependent angular momentum in the direction of the vector
potential intrinsic to the system. Such a realization provides a plausible
context for the experimental confirmation of the elusive gravitational anomaly.Comment: 5 pages, 3 figure
Topological insulating phases in mono and bilayer graphene
We analyze the influence of different quadratic interactions giving rise to
time reversal invariant topological insulating phases in mono and bilayer
graphene. We make use of the effective action formalism to determine the
dependence of the Chern Simons coefficient on the different interactions
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