Optical excitations in a quarter-filled Ni(dmit)2 based compound described by a dimerized octamer model

The reflectance spectra of [SMe3][Ni(dmit)2 (dmit=1,3-dithiole-2 thione-4,5-dithiolato), quarter-filled organic conductor with strongly dimerized structure, will be discussed in the framework of the new Raman results for this compound. The spectra are interpreted on the basis of a dimerized Hubbard octamer model, which accounts for the low energy electronic transitions and for the coupling of the electronic excitations with the intramolecular vibrations.