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

Well-defined plasma edges appeared in the polarized reflection spectra polarized parallel (//a) and perpendicular (⊥a) to the molecular stack. 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 surface were calculated. The Fermi surfaces of both compounds were open in the kc direction. At low temperature the intra-stack transfer integral increased by about 30 % whereas the enhancement of inter-stack transfer integral was very weak.