T. Vinchon et al., EFFECTS OF COULOMB INTERACTIONS ON THE ELECTRONIC-STRUCTURE OF THE SI(001) SURFACE, Physical review. B, Condensed matter, 48(11), 1993, pp. 8190-8202
The electronic structure of the Si(001) surface is obtained with a tig
ht-binding method developed in the slab geometry. The effects of local
Coulomb interactions on the stability of antiferromagnetic solutions
and on the width of the gap in the surface states at the Si(001) surfa
ce reconstructed with symmetric dimers are first visualized with a two
-orbital model Hamiltonian. It allows us to study the effect of the co
upling between the dangling and the bonding orbitals. The calculation
performed with the tight-binding method supports the results of the mo
del and provides an explanation of the semiconducting character of the
reconstructed Si(001) surface with symmetric dimers. For realistic pa
rameters which include the atomic values of the interorbital exchange,
an antiferromagnetic order of (2 x 2) symmetry is stable. It is argue
d that even if the long-range antiferromagnetic order is destabilized
by quantum fluctuations in quasi-two-dimensional surface states, the s
hort-range antiferromagnetic order induced in the dangling orbitals by
Coulomb interactions is sufficient to explain the semiconducting beha
vior of symmetric dimers.