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

We report the results of a detailed study of the field orientation dependen ce 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 orientatio n dependence of the sign and phase of the fundamental alpha frequency, at f ields 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 approximat ely constant. This implies that spin splitting cannot occur within the low- magnetic-field phase until the angle between the magnetic held and the norm al to the conducting planes is similar to 42 degrees. This finding contrast s greatly with that recently published by Sasaki and Fukase. The results of the present study imply that the electron-electron interactions are largel y field independent in this material, while a field dependence of the elect ron-phonon interactions is still tenable. The manner in which the amplitude of the wave form of the oscillations is damped within the low-magnetic-hel d phase is suggestive of a nonharmonically indexed reduction of the amplitu de, thereby eliminating explanations in terms of magnetic breakdown or impu rity scattering. Meanwhile, the presence of a large amplitude second harmon ic within the low-magnetic-field phase that has a negative sign over a broa d range of angles can be explained only by the frequency doubling effect.