Optical conductivity of bilayer graphene with and without an asymmetry gap

Abstract

When a bilayer of graphene is placed in a suitably configured field effect device, an asymmetry gap can be generated and the carrier concentration made different in each layer. This provides a tunable semiconducting gap, and the valence and the conductance band no longer meet at the two Dirac points of the graphene Brillouin zone. We calculate the optical conductivity of such a semiconductor with particular emphasis on the optical spectral weight redistribution brought about by changes in gap and chemical potential due to charging. We derive an algebraic formula for arbitrary value of the chemical potential for the case of the bilayer conductivity without a gap.

Structure of graphene and its disorders: a review

“…The single spin Hamiltonians for AA-stacked and AB-stacked bilayer graphene and their corresponding matrix representations are given in Refs [157,158]. By calculation of the eigenvalues of these two matrices, the band structures of two types of bilayer are obtained and the corresponding low-energy parts are plotted in Figure 9(e,g).…”

“…Moreover, the formation of closed edges between adjacent graphene layers results in that AA stacking is more frequently seen in bilayer graphene so that the local strains can be reduced [164]. Further, extensive theoretical and experimental studies have been carried out to explore the properties of AA-stacked [157,164–166] and Bernal-stacked [139,158,167,168] bilayer graphenes.…”

Nonlinear optical spectrum of bilayer graphene in the terahertz regime

“…21 By including the second most dominant interlayer coupling, some unusual properties such as a peculiar Landau-level spectrum have been derived, 16 as well as a new low energy peak in the optical conductance. 22,23 By further increasing the layer numbers, one has graphene multilayers whose energy dispersion near the K-point can be tuned by a gate voltage. 24 Graphene exhibits strong optical response.…”

Optical conductivity of hydrogenated graphene from first principles

“…The optical conductivity is another property investigated both theoretically and experimentally for many graphene-based systems such as single [40][41][42][43][44] and few layer graphene [45,46], graphite [47][48][49], and carbon nanotubes [50].…”