15,253 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.
Bremsstrahlung radiation from the interaction of short laser pulses with dielectrics
An intense, short laser pulse incident on a transparent dielectric can excite
electrons from valence to the conduction band. As these electrons undergo
scattering, both from phonons and ions, they emit bremsstrahlung radiation.
Here we present a theory of bremsstrahlung emission appropriate for laser
pulse-dielectric interactions. Simulations of the interaction, incorporating
this theory, illustrate characteristics of the radiation (power, energy and
spectra) for arbitrary ratios of electron collision frequency to radiation
frequency. The conversion efficiency of laser pulse energy into bremsstrahlung
radiation depends strongly on both the intensity and duration of the pulse,
saturating at values of about 10e-5. Depending on whether the intensity is
above or below the damage threshold of the material, the emission can originate
either from the surface or the bulk of the dielectric respectively. The
bremsstrahlung emission may provide a broadband light source for diagnostics
Gauge model at finite temperature with massive quarks and at finite density on anisotropic lattice
Critical properties of QCD and the chiral condensate at finite density are
analytically studied on an anisotropic lattice in the approximation SU(N)
\simeq Z(N). Asymptotic behavior of the partition function and its continuum
limit are discussed.Comment: talk given by L.A.Averchenkova at LATTICE'98, Boulder, CO, USA, 13-18
July 1998, 3 pages, LaTex, no figure
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