1,134 research outputs found
Modulation of Kekul\'e adatom ordering due to strain in graphene
Intervalley scattering of carriers in graphene at `top' adatoms may give rise
to a hidden Kekul\'e ordering pattern in the adatom positions. This ordering is
the result of a rapid modulation in the electron-mediated interaction between
adatoms at the wavevector , which has been shown experimentally and
theoretically to dominate their spatial distribution. Here we show that the
adatom interaction is extremely sensitive to strain in the supporting graphene,
which leads to a characteristic spatial modulation of the Kekul\'e order as a
function of adatom distance. Our results suggest that the spatial distributions
of adatoms could provide a way to measure the type and magnitude of strain in
graphene and the associated pseudogauge field with high accuracy.Comment: 9 pages, 7 figure
Electron-induced rippling in graphene
We show that the interaction between flexural phonons, when corrected by the
exchange of electron-hole excitations, may place the graphene sheet very close
to a quantum critical point characterized by the strong suppression of the
bending rigidity of the membrane. Ripples arise then due to spontaneous
symmetry breaking, following a mechanism similar to that responsible for the
condensation of the Higgs field in relativistic field theories. In the presence
of membrane tensions, ripple condensation may be reinforced or suppressed
depending on the sign of the tension, following a zero-temperature buckling
transition in which the order parameter is given essentially by the square of
the gradient of the flexural phonon field.Comment: 4 pages, 3 figure
Aharonov-Bohm oscillations of a particle coupled to dissipative environments
The amplitude of the Bohm-Aharonov oscillations of a particle moving around a
ring threaded by a magnetic flux and coupled to different dissipative
environments is studied. The decay of the oscillations when increasing the
radius of the ring is shown to depend on the spatial features of the coupling.
When the environment is modelled by the Caldeira-Leggett bath of oscillators,
or the particle is coupled by the Coulomb potential to a dirty electron gas,
interference effects are suppressed beyond a finite length, even at zero
temperature. A finite renormalization of the Aharonov-Bohm oscillations is
found for other models of the environment.Comment: 6 page
Dynamics of Holes and Universality Class of the Antiferromagnetic Transition in the Two Dimensional Hubbard Model
The dynamics of a single hole (or electron) in the two dimensional Hubbard
model is investigated. The antiferromagnetic background is described by a
N\`eel state, and the hopping of the carrier is analyzed within a configuration
interaction approach. Results are in agreement with other methods and with
experimental data when available. All data are compatible with the opening of a
mean field gap in a Fermi liquid of spin polarons, the so called Slater type of
transition. In particular, this hypothesis explains the unusual dispersion
relation of the quasiparticle bands near the transition. Recent photoemission
data for CaCuOCl are analyzed within this context.Comment: New results and comparison with recent data adde
Transverse transport in graphite
Graphite is a layered material showing a strong anisotropy. Among the
unconventional properties reported by experiments, the electronic transport
along the c-axis, which has direct implications in order to build graphitic
devices, remains a controversial topic. We study the influence of inelastic
scattering on the electron tunnelling between layers. In the presence of
electron electron interactions, tunnelling processes are modified by inelastic
scattering events.Comment: 9 pages, no figures Proceedings of the Graphene Conference, MPI PKS
Dresden, September 200
Pseudomagnetic fields and ballistic transport in a suspended graphene sheet
We study a suspended graphene sheet subject to the electric field of a gate
underneath. We compute the elastic deformation of the sheet and the
corresponding effective gauge field, which modifies the electronic transport.
In a clean system the two-terminal conductance of the sample is reduced below
the ballistic limit and is almost totally suppressed at low carrier
concentrations in samples under tension. Residual disorder restores a small
finite conductivity.Comment: 4 page
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