Electronic properties of a biased graphene bilayer

• Published in: Journal of physics. Condensed matter Vol. 22; no. 17; p. 175503
• Main Authors: Castro, Eduardo V, Novoselov, K S, Morozov, S V, Peres, N M R, Lopes dos Santos, J M B, Nilsson, Johan, Guinea, F, Geim, A K, Castro Neto, A H
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 05.05.2010; Institute of Physics
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron states and collective excitations in thin films, multilayers, quantum wells, mesoscopic and nanoscale systems; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Physics; Thin films and multilayers; Continuum; External fields; Screening; Energy gap; Electronic structure; Silicon carbide; Charge screening; Tight binding approximation; Graphene; Electric field effects; Cyclotron resonance; Bilayers
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/22/17/175503

We study, within the tight-binding approximation, the electronic properties of a graphene bilayer in the presence of an external electric field applied perpendicular to the system-a biased bilayer. The effect of the perpendicular electric field is included through a parallel plate capacitor model, with screening correction at the Hartree level. The full tight-binding description is compared with its four-band and two-band continuum approximations, and the four-band model is shown to always be a suitable approximation for the conditions realized in experiments. The model is applied to real biased bilayer devices, made out of either SiC or exfoliated graphene, and good agreement with experimental results is found, indicating that the model is capturing the key ingredients, and that a finite gap is effectively being controlled externally. Analysis of experimental results regarding the electrical noise and cyclotron resonance further suggests that the model can be seen as a good starting point for understanding the electronic properties of graphene bilayer. Also, we study the effect of electron-hole asymmetry terms, such as the second-nearest-neighbour hopping energies t' (in-plane) and γ(4) (inter-layer), and the on-site energy Δ.