669 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
Full counting statistics of a charge pump in the Coulomb blockade regime
We study the full charge counting statistics of a charge pump based on a
nearly open single electron transistor. The problem is mapped onto an exactly
soluble problem of a g=1/2 non-equilibrium Luttinger liquid with an impurity.
We obtain an analytic expression for the generating function of the transmitted
charge for an arbitrary pumping strength. Even though this model contains
fractionally charged excitations only integer transmitted charges can be
observed during finite observation times.Comment: 4 pages, 1 figur
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