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

Abstract

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.

REVTeX, 24 pages, 9 figures included. Submitted to Phys. Rev. B