We have performed angle-resolved photoemission spectroscopy on (PbSe) 5(Bi2Se3)3m, which forms a natural multilayer heterostructure consisting of a topological insulator and an ordinary insulator. For m=2, we observed a gapped Dirac-cone state within the bulk band gap, suggesting that the topological interface states are effectively encapsulated by block layers; furthermore, it was found that the quantum confinement effect of the band dispersions of Bi2Se3 layers enhances the effective bulk band gap to 0.5eV, the largest ever observed in topological insulators. For m=1, the Dirac-like state is completely gone, suggesting the disappearance of the band inversion in the Bi2Se 3 unit. These results demonstrate that utilization of naturally occurring heterostructures is a new promising strategy for manipulating the topological states and realizing exotic quantum phenomena.
ASJC Scopus subject areas
- Physics and Astronomy(all)