14,361 research outputs found
Conductivity of graphene in the framework of Dirac model: Interplay between nonzero mass gap and chemical potential
The complete theory of electrical conductivity of graphene at arbitrary
temperature is developed with taken into account mass-gap parameter and
chemical potential. Both the in-plane and out-of-plane conductivities of
graphene are expressed via the components of the polarization tensor in
(2+1)-dimensional space-time analytically continued to the real frequency axis.
Simple analytic expressions for both the real and imaginary parts of the
conductivity of graphene are obtained at zero and nonzero temperature. They
demonstrate an interesting interplay depending on the values of mass gap and
chemical potential. In the local limit, several results obtained earlier using
various approximate and phenomenological approaches are reproduced, refined and
generalized. The numerical computations of both the real and imaginary parts of
the conductivity of graphene are performed to illustrate the obtained results.
The analytic expressions for the conductivity of graphene obtained in this
paper can serve as a guide in the comparison between different theoretical
approaches and between experiment and theory.Comment: 27 pages, 5 figures; accepted for publication in Phys. Rev.
Transient currents in a molecular photo-diode
Light-induced charge transmission through a molecular junction (molecular
diode) is studied in the framework of a HOMO-LUMO model and in using a kinetic
description. Expressions are presented for the sequential (hopping) and direct
(tunneling) transient current components together with kinetic equations
governing the time-dependent populations of the neutral and charged molecular
states which participate in the current formation. Resonant and off-resonant
charge transmission processes are analyzed in detail. It is demonstrated that
the transient currents are associated with a molecular charging process which
is initiated by photo excitation of the molecule. If the coupling of the
molecule to the electrodes is strongly asymmetric the transient currents can
significantly exceed the steady state current.Comment: 17 pages, 12 figures, accepted for publication in Chemical Physic
Scattering properties of weakly bound dimers of fermionic atoms
We consider weakly bound diatomic molecules (dimers) formed in a
two-component atomic Fermi gas with a large positive scattering length for the
interspecies interaction. We develop a theoretical approach for calculating
atom-dimer and dimer-dimer elastic scattering and for analyzing the inelastic
collisional relaxation of the molecules into deep bound states. This approach
is based on the single-channel zero range approximation, and we find that it is
applicable in the vicinity of a wide two-body Feshbach resonance. Our results
draw prospects for various interesting manipulations of weakly bound dimers of
fermionic atoms.Comment: extended version of cond-mat/030901
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