Electron spectrum of double-sheet graphene with broken equivalence of sublattices within layers

The electron spectrum of double-sheet graphene composed of sheets with broken equivalence of sublattices, i.e., of gapped (with the gap width $2\Delta$) graphene sheets, has been calculated. There is a band gap with the width $2\Delta$ in the spectrum of such a system. The influence of the transverse electric field on the electron spectrum of this system has been investigated. It has been shown that the gap width in the presence of the electric field is proportional to the difference $|U-\Delta|$; i.e., the gap vanishes at $U=\Delta$. This effect can be suggested as an effective method of eliminating an unwanted gap in the spectrum.