Metal-insulator transition for K on GaAs(100)-As rich surfaces

Recent LD-LCAO (local density-linear combination of atomic orbitals) calculations show that atoms deposited on the As-rich GaAs(100)-2 x 4 reconstructed surface tend to form quasi one-dimensional structures along the missing rows of the semiconductor surface. We show that the 'conduction' band associated with the K-orbitals may be described by an effective extended Hubbard Hamiltonian. Using Green functions techniques we study the metal-insulator transition within this model, which allows us to establish the metallic or insulating character of a given one-dimensional structure. We find that the transition into the metallic phase takes place when going from 5/8 to 7/8 monolayers.