REFLECTANCE SPECTRA OF KAPPA-(BEDT-TTF)2X

We have measured reflectance spectra of several kappa-type BEDT-TTF salts in order to investigate their electronic structures. The line shape of the reflectance spectra are all alike in these salts, regardless of their electrical properties. On the other hand, the low-temperature spectra of these salts show considerable difference. Among all, the spectra of kappa-(BEDT-TTF)2Ag(CN)2.H2O salt are completely different from those of other kappa-type salts. Its plasma frequencies of intra-band transition obtained by the Drude-Lorentz fit of the reflectance spectra are 0.33eV for E//b and 0.34eV for E//c, respectively, which are comparable to the half of the plasma frequencies already obtained in other kappa-type salt. In this article we present a model which explains the anomalous reflection spectra found in this salt.