Band structure of (BDT-TTP)(2)X (X=SbF6, AsF6, ClO4) studied by reflectionspectroscopy

Well-defined plasma edges appeared in the polarized reflection spectra pola rized parallel (11a) and perpendicular (perpendicular to a)the molecular st ack. The intra- and inter-stack transfer integrals were estimated from the plasma frequencies in the framework of tight-binding model. Based on these transfer integrals, the energy dispersion, density of state, and Fermi surf ace were calculated. The Fermi surfaces of both compounds were open in the k(c) direction. At low temperature the intra-stack transfer integral increa sed by about 30 % whereas the enhancement of inter-stack transfer integral was very weak.