Effect of interactions on determination of Fermi surfaces

The effect of both electron-electron and electron-phonon interactions on a degenerate electron gas in a uniform positive background is considered. It is shown that when electron-electron interactions alone are considered the free-electron mass is still measured by cyclotron resonance, the Faraday effect, and optical constants. However, the period of the de Haas-van Alphen oscillations is changed from what one calculates neglecting interactions and is changed in the same way that the specific heat is. When electron-phonon interactions are added everything changes. In particular, it is shown that the cyclotron mass is no longer the free value, and the de Haas-van Alphen period and the specific heat are changed in different ways. Comparison with measurements on aluminum which approximates the model used shows that both electron-phonon and electron-electron effects are important and of the same magnitude.