Substrate, a choice of engineering the pseudospin in graphene

Abstract

Structure and symmetry of crystal dictate their physical properties. Reasonable manipulation of those parameters allows designing the materials’ properties in a nonchemical way, like the strain or pressure. Here we report the possibility of manipulating the pseudospin and lifting its degeneracy through the substrate corrugation in graphene, which directly relates to the chirality of Dirac fermions in the low energy regime. By a detailed scanning tunneling microscopy (STM) study that combined with van der Waals heterostructure fabrications, we find the pseudospin degeneracy can be continually lifted that materialized as the gradual wavefunction polarization on the two sublattices by changing graphene’s curvature through a bump. Strikingly, the sublattice polarization shows a linear dependence on the geometry of bumps, which enables to extract a pseudo-g-factor to characterize the pseudospin splitting and geometry. Our results may shine light on engineering the pseudospin, the new degree of freedom, by a mechanical path.