Tunable Excitons in Biased Bilayer Graphene

Abstract

Recent measurements have shown that a continuously tunable bandgap of up to 250 meV can be generated in biased bilayer graphene [Y. Zhang et al., Nature 459, 820 (2009)], opening up pathway for possible graphene-based nanoelectronic and nanophotonic devices operating at room temperature. Here, we show that the optical response of this system is dominated by bound excitons. The main feature of the optical absorbance spectrum is determined by a single symmetric peak arising from excitons, a profile that is markedly different from that of an interband transition picture. Under laboratory conditions, the binding energy of the excitons may be tuned with the external bias going from zero to several tens of meV's. These novel strong excitonic behaviors result from a peculiar, effective ``one-dimensional'' joint density of states and a continuously-tunable bandgap in biased bilayer graphene. Moreover, we show that the electronic structure (level degeneracy, optical selection rules, etc.) of the bound excitons in a biased bilayer graphene is markedly different from that of a two-dimensional hydrogen atom because of the pseudospin physics.

References in corpus (16)

• The electronic properties of graphene
• Biased bilayer graphene: semiconductor with a gap tunable by electric field effect
• Gate-induced insulating state in bilayer graphene devices
• Asymmetry gap in the electronic band structure of bilayer graphene
• Excitonic Effects on the Optical Response of Graphene and Bilayer Graphene
• Electronic states and Landau levels in graphene stacks
• Ab Initio Theory of Gate Induced Gaps in Graphene Bilayers
• Optical and magneto-optical far-infrared properties of bilayer graphene
• Dependence of band structures on stacking and field in layered graphene
• Determination of the electronic structure of bilayer graphene from infrared spectroscopy results
• Infrared spectroscopy of electronic bands in bilayer graphene
• Optical conductivity of bilayer graphene with and without an asymmetry gap
• Transmission through a biased graphene bilayer barrier
• Formation of p-n junction in polymer electrolyte-top gated bilayer graphene transistor
• Gaped graphene bilayer: disorder and magnetic field effects
• Robustness of the optical-conductivity sum rule in Bilayer Graphene

Cited by in corpus (2)

• Wafer Scale Homogeneous Bilayer Graphene Films by Chemical Vapor Deposition
• Excitons and Optical Absorption on the Surface of a Strong Topological Insulator with a Magnetic Energy Gap