Diagonal and off-diagonal correlation effects in anderson-localized states

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Abstract
The present paper discusses a general theoretical model which treats the interplay of randomness and electron correlation in Anderson-localized states. In constructing the model Hamiltonian, the behaviour of localized states with an envelope function is explicitly taken into account. The calculated results of spin susceptibility and electronic specific heat as well as density of states are presented. It is shown that the diagonal correlation gives rise to the occurrence of singly occupied states below the Fermi energy, E F, and that this results in a Curie-type susceptibility at low temperatures. As a consequence of the variation of the correlation energy from state to state, the density of doubly occupied states becomes large near E F. It is also shown that the off-diagonal correlation effect gives rise to a kinetic exchange interaction between singly occupied states, which favours spin-singlet states.

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