Tuesday, March 17, 2015
Abstract-Negative terahertz conductivity in disordered graphene bilayers with population inversion
The gapless energy band make the structures based on and bilayer with the population inversion to be promising media for the interband terahertz (THz) lasing. However, a strong intraband absorption at THz frequencies still poses a challenge for efficient THz lasing. In this paper, we show that in the pumped bilayer, the indirect interband radiative accompanied by of carriers by disorder can provide a substantial negative contribution to the THz conductivity (together with the direct interband In the bilayer on high- substrates with point defects, these substantially compensate the losses due to the intraband (Drude) absorption. We also demonstrate that the indirect interband contribution to the THz conductivity in a bilayer with the extended defects (such as the impurity clusters) can surpass by several times the fundamental limit associated with the direct interband and the Drude conductivity as well. These predictions can affect the strategy of the graphene-based THz laser implementation.