摘要
Here we report the evolution of bulk band structure and surface states in rare-earth monobismuthides with partially filled f shell. Utilizing synchrotron-based photoemission spectroscopy, we determined the three-dimensional bulk band structure and identified the bulk band inversions near the X points, which, according to the topological theory, could give rise to nontrivial band topology with an odd number of gapless topological surface states. Near the surface Γ point, no clear evidence for a predicted gapless topological surface state is observed due to its strong hybridization with the bulk bands. Near the M point, the two surface states, because of projections from two inequivalent bulk band inversions, interact and give rise to two peculiar sets of gapped surface states. The bulk band inversions and corresponding surface states can be tuned substantially by varying rare-earth elements, in good agreement with density-functional theory calculations assuming local f electrons. Our study therefore establishes rare-earth monobismuthides as an interesting class of materials possessing tunable electronic properties and magnetism, providing a promising platform to search for various properties in potentially correlated topological materials.