Hybridization of electron subbands in a double quantum well at quantizing magnetic field

V. T. Dolgopolov, A. A. Shashkin, E. V. Deviatov, F. Hastreiter, M. Hartung, A. Wixforth, K. L. Campman, A. C. Gossard

Published 1998-06-17Version 1

We employ magnetocapacitance and far-infrared spectroscopy techniques to study the spectrum of the double-layer electron system in a parabolic quantum well with a narrow tunnel barrier in the centre. For gate-bias-controlled asymmetric electron density distributions in this soft two-subband system we observe both individual subband gaps and double layer gaps at integer filling factor $\nu$. The bilayer gaps are shown to be either trivial common for two subbands or caused by hybridization of electron subbands in magnetic field. We describe the observed hybrid gaps at $\nu=1$ and $\nu=2$ within a simple model for the modified bilayer spectrum.