Charge Transfer Instability with Structural Change. I. Two-Sites Two-Electrons System

抄録

Charge transfer instability with structural change is studied with a simplest two-sites two-electrons model which allows exact treatment in the whole range of electron transfer energy T, on-site Coulomb energy U and the lattice stabilization energy S. The instability takes place when S overcomes T or U, the transition being of the second order for S-T competition and the first order for S-U competition, with a critical point inside the T-U-S triangle. The excited state is subject to instability with even smaller values of S. The effect of dimensionality on the nature of the transition is briefly discussed.