Semimetal Na₃Bi thin film grown on double-layer graphene by molecular beam epitaxy

Atomically flat thin films of topological semimetal Na₃ Bi are grown on double-layer graphene formed on 6H-SiC(0001) substrates by molecular beam epitaxy. By combined techniques of molecular beam epitaxy, scanning tunneling microscopy and angle resolved photoelectron spectroscopy, the growth conditions for Na₃ Bi thin films on double-layer graphene are successfully established. The band structure of Na₃ Bi grown on graphene is mapped along Γ-M and Γ-K directions. Furthermore, the energy band of Na₃ Bi at higher energy is uncovered by doping Cs atoms on the surface.