1,243,685 research outputs found
Anisotropic conductivity of doped graphene due to short-range non-symmetric scattering
The conductivity of doped graphene is considered taking into account
scattering by short-range nonsymmetric defects, when the longitudinal and
transverse components of conductivity tensor appear to be different. The
calculations of the anisotropic conductivity tensor are based on the
quasiclassical kinetic equation for the case of monopolar transport at low
temperatures. The effective longitudinal conductivity and the transverse
voltage, which are controlled by orientation of sample and by gate voltage
(i.e. doping level), are presented.Comment: 3 pages, 2 figure
Transfer-matrix study of a hard-square lattice gas with two kinds of particles and density anomaly
Using transfer matrix and finite-size scaling methods, we study the
thermodynamic behavior of a lattice gas with two kinds of particles on the
square lattice. Only excluded volume interactions are considered, so that the
model is athermal. Large particles exclude the site they occupy and its four
first neighbors, while small particles exclude only their site. Two
thermodynamic phases are found: a disordered phase where large particles occupy
both sublattices with the same probability and an ordered phase where one of
the two sublattices is preferentially occupied by them. The transition between
these phases is continuous at small concentrations of the small particles and
discontinuous at larger concentrations, both transitions are separated by a
tricritical point. Estimates of the central charge suggest that the critical
line is in the Ising universality class, while the tricritical point has
tricritical Ising (Blume-Emery-Griffiths) exponents. The isobaric curves of the
total density as functions of the fugacity of small or large particles display
a minimum in the disordered phase.Comment: 9 pages, 7 figures and 4 table
The structure of the graviton self-energy at finite temperature
We study the graviton self-energy function in a general gauge, using a hard
thermal loop expansion which includes terms proportional to T^4, T^2 and
log(T). We verify explicitly the gauge independence of the leading T^4 term and
obtain a compact expression for the sub-leading T^2 contribution. It is shown
that the logarithmic term has the same structure as the ultraviolet pole part
of the T=0 self-energy function. We argue that the gauge-dependent part of the
T^2 contribution is effectively canceled in the dispersion relations of the
graviton plasma, and present the solutions of these equations.Comment: 27 pages, 6 figure
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