Origin of the split quantum oscillation wave form in α-(BEDT-TTF)2KHg(SCN)4 -: art. no. 195102

We report the results of a detailed study of the field orientation dependence of the de Haas-van Alphen wave form in alpha-( BEDT-TTF)(2)KHg( SCN)(4) over a wide range of angles and fields. By considering the field orientation dependence of the sign and phase of the fundamental alpha frequency, at fields both well above and below the kink transition field, it is found that the product of the effective mass with the electron g factor is approximately constant. This implies that spin splitting cannot occur within the low-magnetic-field phase until the angle between the magnetic field and the normal to the conducting planes is similar to 42 degrees. This finding contrasts greatly with that recently published by Sasaki and Fukase. The results of the present study imply that the electron-electron interactions are largely field independent in this material, while a field dependence of the electron-phonon interactions is still tenable. The manner in which the amplitude of the wave form of the oscillations is damped within the low-magnetic-field phase is suggestive of a nonharmonically indexed reduction of the amplitude, thereby eliminating explanations in terms of magnetic breakdown or impurity scattering. Meanwhile, the presence of a large amplitude second harmonic within the low-magnetic-field phase that has a negative sign over a broad range of angles can be explained only by the frequency doubling effect.