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J. Phys.: Condens. Matter 4 (1992) pp. 8477-8488

The surface state-surface resonance transition on Ta(011)

J.B.A.N. van Hoof, S. Crampin and J.E. Inglesfield

Institute for Theoretical Physics, Catholic University of Nijmegen, Toernooiveld, NL-6525 ED Nijmegen, The Netherlands

Abstract
We study an unusual surface state-surface resonance transition recently identified in photoemission on Ta(011) using surface electronic structure calculations performed with the surface embedded Green function method. The transition is understood in terms of the relative movement of the bulk bands and surface potential with increasing parallel momentum, which switches the condition for a surface state below the band at the zone centre to a resonance within the band beyond 0.11 inverse Angstrom along Gamma-bar. A simple two-band model is constructed to illustrate the effect. Comparison of the calculated and experimental surface bands away from the zone centre shows sizeable differences, and we predict the existence of several unnocupied surface states which should be visible to inverse photoemission.