Broken symmetry states in n-type silicon inversion layers

A detailed examination of the possible intervalley electron-electron interactions in n-type silicon inversion layers leads to a model Hamiltonian of considerably greater complexity than that studied by Kelly and Falicov. While the theory of broken-symmetry states retains its structure, significant new points of detail emerge. At zero stress at the Si(111)/SiO 2 interface, all six valleys participate in the ground state; but quite small stresses suffice to destroy such a state, while at the Si(100)/SiO 2 interface a broken-symmetry state at intermediate stress is rather easier to stabilise.