Electron subbands in a double quantum well in a quantizing magnetic field

We employ magnetocapacitance and far-infrared spectroscopy techniques to st udy the spectrum of the double-layer electron system in a parabolic quantum well with a narrow tunnel barrier in the center. For gate-bias-controlled asymmetric electron density distributions in this soft two-subband system w e observe both individual subband gaps and double-layer gaps at integer fil ling factor v. The bilayer gaps are shown to be either trivially common for two subbands or caused by the wavefunction reconstruction in growth direct ion as induced by intersubband electron transfer at a normal to the interfa ce magnetic field. In the latter case the observed gaps at v = 1 and v = 2 are described within a simple model for the modified bilayer spectrum. [S01 63-1829(99)11319-5].