FAR-INFRARED CYCLOTRON-RESONANCE STUDY OF ELECTRON DYNAMICS IN (BEDT-TTF) 2KHG(SCN)4

We report the first measurement of cyclotron resonance in a metallic charge-transfer salt. Carrier pockets are observed with effective masses of 0.40m(e) and 0.94m(e). In contrast, masses of 2.0m(e) and 2.4m(e) are seen in magnetotransport. We propose that the transport masses are enhanced by electron-electron interactions, whereas, following Kohn's theorem, the mass measured by cyclotron resonance is independent of these interactions. These measurements therefore represent the first direct gauge of the electron-electron interaction in a metallic charge-transfer salt.