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Abstract:
Developing graphene-based nanoelectronics hinges on opening a band gap
in the electronic structure of graphene, which is commonly achieved by
breaking the inversion symmetry of the graphene lattice via an electric
field (gate bias) or asymmetric doping of graphene layers. Here we
introduce a new design strategy that places a bilayer graphene sheet
sandwiched between two cladding layers of materials that possess strong
spin-orbit coupling (e.g., Bi2Te3). Our ab initio and tight-binding
calculations show that a proximity enhanced spin-orbit coupling effect
opens a large (44 meV) band gap in bilayer graphene without breaking its
lattice symmetry, and the band gap can be effectively tuned by an
interlayer stacking pattern and significantly enhanced by interlayer
compression. The feasibility of this quantum-well structure is
demonstrated by recent experimental realization of high-quality
heterojunctions between graphene and Bi2Te3, and this design also
conforms to existing fabrication techniques in the semiconductor
industry. The proposed quantum-well structure is expected to be
especially robust since it does not require an external power supply to
open and maintain a band gap, and the cladding layers provide protection
against environmental degradation of the graphene layer in its device
applications.
