Twisted bilayer graphene with a twist angle of around 1.1° features a pair of isolated flat electronic bands and forms a platform for investigating strongly correlated electrons. Here, we use scanning tunnelling microscopy to probe the local properties of highly tunable twisted bilayer graphene devices and show that the flat bands deform when aligned with the Fermi level. When the bands are half-filled, we observe the development of gaps originating from correlated insulating states. Near charge neutrality, we find a previously unidentified correlated regime featuring an enhanced splitting of the flat bands. We describe this within a microscopic model that predicts a strong tendency towards nematic ordering. Our results provide insights into symmetry-breaking correlation effects and highlight the importance of electronic interactions for all filling fractions in twisted bilayer graphene.

扭曲角约为1.1°的扭曲双层石墨烯具有一对孤立的平坦电子带，并形成了一个研究强相关电子的平台。在这里，我们使用扫描隧道显微镜来探测高度可调的扭曲双层石墨烯器件的局部特性，并显示当与费米能级对准时，平坦带会变形。当带被半填充时，我们观察到由相关绝缘状态引起的间隙的发展。在接近电荷中性的情况下，我们发现了以前未知的相关机制，其特征在于平坦频带的增强分裂。我们在微观模型中描述了这一点，该模型预测了向列有序的强烈趋势。