FERMI-SURFACE STUDY OF ALPHA-(BEDT-TTF)(2)MHG(SCN)(4) BY CYCLOTRON-RESONANCE MEASUREMENT

We performed cyclotron resonance (CR) measurements of alpha-(BEDT-TTF) (2)MHg(SCN)(4) (M = Rb, K) in the density-wave state. We applied the m agnetic field perpendicular to the conducting ac-plane and we measured the angle dependence of the cyclotron resonance absorption. The obser ved four resonances in M = Rb salt showed 1/cos theta dependence, wher e the field was inclined by the angle theta from the direction perpend icular to the ac-plane. This dependence clearly shows that observed fo ur resonances in M = Rb salt are CR's. The CR measurement of M = K sal t was also performed and the results are also presented. To our surpri se, obtained effective masses for M = K salt at 1.8 K were different f rom those obtained for M = Rb salt. (C) 1998 Elsevier Science B.V. All rights reserved.