Unoccupied surface states of LaB6(001) studied by k-resolved inverse photoemission

We have measured k-resolved inverse photoemission spectra of LaB6(001) to study unoccupied surface states. The surface states are observed near the Fermi level (E-F) and at 6.8 eV above E-F, which are originated from La 5d and La 4f states, respectively. The surface state near E-F shows energy dispersion along the Gamma-M direction of the surface Brillouin zone, which does not agree with that of a recently reported theoretical calculation. It is deduced that at a LaB6(001) surface, electrons are transferred from the subsurface to the topmost La layer. This charge redistribution can reduce surface dipole moments.