The Optical Conductivity for a Spin-Peierls Ground State of $\hbox {(TMTTF)}_{2}\hbox {PF}_{6}$ with Tetramer Formation

Abstract

We theoretically investigate the optical conductivity of $\hbox {(TMTTF)}_{2}\hbox {PF}_{6}$ in the spin-Peierls ground state within the framework of the exact diagonalization method at absolute zero temperature ($T=0$). As an effective model, a 1/4-filled 1D (one-dimensional) extended Hubbard model with tetramerization is employed. Using appropriate parameters of the model which have already been reported, we clarify the electronic photoexcitation energies from the spin-Peierls ground state. Since some experiments indicate the formation of a tetramer in the spin-Peierls ground state of $\hbox {(TMTTF)}_{2}\hbox {PF}_{6}$, our results are useful to understand the effects of tetramerization on the optical properties of $\hbox {(TMTTF)}_{2}\hbox {PF}_{6}$.