Exploring bilayer graphene lateral quantum structures for valley filtering

Abstract

Energy bands in AB-stacked bilayer graphene are featured by the co-presence of trigonal warping and a Mexican hat structure around each Dirac point, and electrically modulatable band edges with the modulation valley-dependent (valley-independent) in the case of in-plane (vertical) fields. This theoretical work takes into account the foregoing realistic features and exploits them for valleytronic applications. Specifically, it investigates in detail electrical valley transport in the armchair direction, in AB-stacked bilayer graphene lateral quantum structures with an interface, a single barrier, and double barriers, respectively, and demonstrates that due to the band structure features as well as an involved interplay among them, such structures harbor an interesting potential for valley filtering. An analysis of transmitted current valley polarization is provided. Optimization of the structures for the polarization is explored. The thermal effect on valley filtering is examined. Sizable polarizations of 88% (97%) and 23% (27%) at low and room temperatures, respectively, are shown to be achievable in the case of one-barrier (double-barrier) structures.