The electron density of surface states has been calculated for both the paramagnetic and the antiferromagnetic states of Si(111). Many-body effects associated with correlation and electron-phonon coupling are included. Our results have been obtained by using a self-consistent tight-binding approach, a Bethe-lattice method, and Green-function techniques. The paramagnetic phase shows a very narrow Kondo-like peak at the Fermi level $E_F$, two satellites at $E_F$±0.2 eV, and two broader peaks at $E_F$±0.8 eV. The antiferromagnetic phase shows two peaks at $E_F$±0.8 eV and two others at $E_F$±0.4 eV. In this case the energy gap of 0.6 eV due to correlation effects is reduced by electron-phonon coupling up to 0.25 eV.

• Received 20 May 1985

DOI:https://doi.org/10.1103/PhysRevB.33.537