670 research outputs found
Effect of electron-electron interactions on the conductivity of clean graphene
Minimal conductivity of a single undoped graphene layer is known to be of the
order of the conductance quantum, independent of the electron velocity. We show
that this universality does not survive electron-electron interaction which
results in the non-trivial frequency dependence. We begin with analyzing the
perturbation theory in the interaction parameter 'g' for the electron
self-energy and observe the failure of the random-phase approximation. The
optical conductivity is then derived from the quantum kinetic equation and the
exact result is obtained in the limit when g << 1 << g ln\omega.Comment: 4 pages, 3 figures; final versio
Minimal conductivity in graphene: interaction corrections and ultraviolet anomaly
Conductivity of a disorder-free intrinsic graphene is studied to the first
order in the long-range Coulomb interaction and is found to be
\sigma=\sigma_0(1+0.01 g), where 'g' is the dimensionless ("fine structure")
coupling constant. The calculations are performed using three different
methods: i) electron polarization function, ii) Kubo formula for the
conductivity, iii) quantum transport equation. Surprisingly, these methods
yield different results unless a proper ultraviolet cut-off procedure is
implemented, which requires that the interaction potential in the effective
Dirac Hamiltonian is cut-off at small distances (large momenta).Comment: 5 pages, 1 figure; Reply to the Comment by I.F. Herbut, V. Juricic,
O. Vafek, and M.J. Case, "Comment on "Minimal conductivity in graphene:
Interaction corrections and ultraviolet anomaly" by Mishchenko E. G.",
arXiv:0809.0725, is added in Appendi
Transport equations for a two-dimensional electron gas with spin-orbit interaction
The transport equations for a two-dimensional electron gas with spin-orbit
interaction are presented. The distribution function is a 2x2-matrix in the
spin space. Particle and energy conservation laws determine the expressions for
the electric current and the energy flow. The derived transport equations are
applied to the spin-splitting of a wave packed and to the calculation of the
structure factor and the dynamic conductivity.Comment: 6 pages, 1 figure, revised versio
Equilibrium currents in chiral systems with non-zero Chern number
We describe simple quantum-mechanical approach to calculating equilibrium
particle current along the edge of a system with non-trivial band spectrum
topology. The approach does not require any a priori knowledge of the band
topology and, as a matter of fact, treats topological and non-topological
contributions to the edge currents on the same footing. We illustrate its
usefulness by demonstrating the existence of `topologically non-trivial'
particle currents along the edges of three different physical systems:
two-dimensional electron gas with spin-orbit coupling and Zeeman magnetic
field, surface state of a topological insulator, and kagome antiferromagnet
with Dzyaloshinskii-Moriya interaction. We describe relation of our results to
the notion of orbital magnetization.Comment: 8 pages, 4 figure
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