title: Unusual microwave response of dirac quasiparticles in graphene.
abstract: Recent experiments have proven that the quasiparticles in graphene obey a Dirac equation. Here we show that microwaves are an excellent probe of their unusual dynamics. When the chemical potential is small, the intraband response can exhibit a cusp around zero frequency Omega and this unusual line shape changes to Drude-like by increasing the chemical potential |mu|, with width linear in mu. The interband contribution at T=0 is a constant independent of Omega with a lower cutoff at 2mu. Distinctly different behavior occurs if interaction-induced phenomena in graphene cause an opening of a gap Delta. At a large magnetic field B, the diagonal and Hall conductivities at small Omega become independent of B but remain nonzero and show a structure associated with the lowest Landau level. This occurs because in the Dirac theory the energy of this level, E0 = +/-Delta, is field independent in sharp contrast to the conventional case.
authors.affiliation: Bogolyubov Institute for Theoretical Physics, Metrologicheskaya Street 14-b, Kiev, 03143, Ukraine.
authors.forename: V P
authors.initials: VP
authors.lastname: Gusynin
authors.forename: S G
authors.initials: SG
authors.lastname: Sharapov
authors.forename: J P
authors.initials: JP
authors.lastname: Carbotte