Phase diagrams of the quantum Sherrington-Kirkpatrick Ising spin glass in a transverse field

Abstract The quantum version of the Sherrington-Kirkpatrick model in a transverse field has been investigated by combining the pair approximation with the discretized path-integral representation. The full phase diagrams are obtained, and the possibilities of the existence of the ferromagnetic, paramagnetic, and spin glass phases are examined without use of the replica method.