Charge-transfer absorption in a dimerized one-dimensional Mott-Hubbard insulator

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Abstract
We investigate interband absorption in dimerized one-dimensional Mott-Hubbard insulators, such as some charge-transfer organic salts, using the Hubbard Hamiltonian. The line-shape function is obtained for the antiferromagnetic ground state by exactly summing to infinite order the moments generated by all possible excursions of the particle and the hole in a projected particle-hole space. The effect of spin disordering is also discussed in terms of a numerical evaluation of moments. It is found that the interband absorption arises from transitions to a sharp intradimer excitonic state as well as to extended band states. The former tends to dominate as the dimerization increases.