Charge density waves in silicon inversion layers: Effect of four valley interaction terms

Kelly and Falicov (KF) have demonstrated that phonon mediated intervalley electronic exchange interactions can lead to a charge density wave type ground state in silicon (111) inversion layers. In their model only two valley interaction terms are included. There are four valley interaction terms which, in principle, are as large in magnitude as the two valley terms. We have investigated the effect of including the four-valley interaction terms on a number of Hartree-Fock solutions.