Department of Physics, Brown University, Providence, RI 02912, USA.
Department of Physics, Harvard University, Cambridge, MA 02138, USA.
Science. 2022 Jan 28;375(6579):437-441. doi: 10.1126/science.abh2889. Epub 2022 Jan 6.
Strong electron correlation and spin-orbit coupling (SOC) can have a profound influence on the electronic properties of materials. We examine their combined influence on a 2-dimensional electronic system at the atomic interface between magic-angle twisted bilayer graphene and a tungsten diselenide crystal. Strong electron correlation within the moiré flatband stabilizes correlated insulating states at both quarter and half filling, and SOC transforms these Mott-like insulators into ferromagnets, evidenced by robust anomalous Hall effect with hysteretic switching behavior. The coupling between spin and valley degrees of freedom is demonstrated through the control of the magnetic order with an in-plane magnetic field, or a perpendicular electric field. Our findings establish an experimental knob to engineer topological properties of moiré bands in twisted bilayer graphene and related systems.
强电子相关和自旋轨道耦合（SOC）会对材料的电子性质产生深远影响。我们研究了它们在魔角扭曲双层石墨烯和二硒化钨晶体原子界面处二维电子系统中的综合影响。莫尔带内的强电子相关在四分之一和半满填充时稳定了关联绝缘态，而 SOC 将这些类莫特绝缘体转变为铁磁体，这一点可以通过具有滞后开关行为的强反常霍尔效应得到证明。自旋和谷自由度之间的耦合可以通过平面内磁场或垂直电场来控制磁有序来实现。我们的发现为在扭曲双层石墨烯和相关系统中设计莫尔带拓扑性质提供了一个实验旋钮。
