Spatial variation of energy gap and Landau levels around gapped bilayer graphene domain walls

Abstract

Bilayer graphene contains, compared to graphene monolayer, an additional graphene sheet and, therefore, extra degrees of freedom, making it a unique system for complex electronic states to emerge. Here, we show that there are two types of domain walls, i.e., coupling domain wall and potential domain wall, in gapped graphene bilayers, which make microscopic electronic properties of the bilayers varying spatially. The coupling domain wall separates two graphene bilayer regions with different interlayer coupling strengths and the potential domain wall is a boundary separating two adjacent regions with different chemical potentials between two layers. We present a microscopically study, using scanning tunnelling microscopy and spectroscopy, around the two types of domain walls. The well-defined domain walls allow us to spatially resolve the energy gap and Landau levels around them, which show novel behaviour beyond what is expected from current theoretical models. Our result indicates that the graphene bilayer may exhibit exotic electronic properties related to the microscopic symmetry of the two layers.