抄録
An analytical and statistically homogeneous cluster theory for elementary excitations in disordered systems is developed on the basis of a graphical method in augmented space. An effective Hamiltonian diagram, preserving the original lattice symmetry and including all overlapping cluster scattering effects, is constructed. The expression for the averaged one-particle Green’s function, which corresponds to an interpolation formula connecting between weak and strong scattering and exhibits a momentum-dependent self-energy, is obtained from that diagram by introducing a Bethe lattice approximation. Calculations of the density of states and the spectral function for simple cubic lattices are presented, and show a better fit to exact numerical results than the single-site coherent potential approximation.
