Origin of combination frequencies in quantum magnetization oscillations of two-dimensional multiband metals

The influence of chemical-potential oscillations on the magnetization oscillations in two-dimensional multiband metals is investigated. In first part, the analytical derivation of Alexandrov and Bratkovsky [Phys. Rev. B 63, 033105 (2001)] of magnetic quantum oscillations in two-dimensional multiband metals with a fixed number of electrons is shown to be mathematically incorrect; the chemical-potential oscillations appearing in the arguments of the Fourier components were not taken into account. In second part, we derive an approximative Fourier series of the magnetization oscillations in the regime of small chemical-potential oscillations. The main result is that combination frequencies with significant amplitudes are found if the individual band frequencies differ significantly.