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