Electronic structure of a bismuth bilayer

Using angle-resolved photoemission spectroscopy, we identified four two-dimensional bands within a 1 eV binding-energy region below the Fermi level. The top two bands that are part of the complex Fermi surface of Bi (111) are located in the projected bulk band gap and exhibit sixfold rotational symmetry of the top Bi bilayer. The two lower-lying bands reside inside the projected bulk band structure. The threefold rotational symmetry of these bands indicates a weak interaction with the underlying bulk bands. Our data can be explained with a tight-binding calculation of a bilayer by eliminating the second nearest-neighbor interactions that determine the coupling between bilayers in bulk Bi.