Experimental observation of the de Haas-van Alphen effect in a multiband quantum-well sample

We report measurements of magnetic quantum oscillations (the de Haas-van Alphen effect) in a quantum well containing more than one subband. The Fourier transform of the magnetization oscillations shows the expected frequencies proportional to the occupancies of each subband, but additional frequency components, in accordance with theoretical predictions of Alexandrov and Bratkovsky, are also detected. These components relate to the sums and differences of the individual subband frequencies, and are a consequence of coupling of the individual subband occupancies due to oscillation of the electrochemical potential with magnetic field in a canonical Fermi system. This is an experimental verification of the Alexandrov and Bratkovsky theory in a multisubband system. [S0163-1829(99)51340-4].