Electronic spectra of AA- and AB- graphene bilayers have been investigated for the case when P-symmetry is broken both inside and between the layers. We have focused special attention on the new regime when the band gaps in different layers have opposite signs. For example, the spectrum of AB bilayer is gapless in the case when band gaps of monolayers are equal in magnitude and opposite in sign. At the same time, such a band gap collapse does not occur in the case of the AA bilayer. We have shown that the gate voltage strongly affects the spectrum of gapped AB bilayers. We use elementary and clear arguments to explain our main results. Finally, we proposed a new and unusual way to determine the type of laying of a graphene bilayer.

已经研究了AA-和AB-石墨烯双层的电子光谱，以了解当P对称性在层内和层间断裂时的情况。当不同层的带隙具有相反的符号时，我们会特别关注新机制。例如，在单层的带隙的大小相等且符号相反的情况下，AB双层的光谱是无间隙的。同时，在AA双层的情况下不会发生这种带隙塌陷。我们已经表明，栅极电压强烈影响带间隙的AB双层的光谱。我们使用基本且清晰的论据来解释我们的主要结果。最后，我们提出了一种新的，不寻常的方法来确定石墨烯双层的铺设类型。