Giant orbital magnetoelectric effect and current-induced magnetization switching in twisted bilayer graphene

• Published in: Nature communications Vol. 11; no. 1; p. 1650
• Main Authors: He, Wen-Yu, Goldhaber-Gordon, David, Law, K. T.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 03.04.2020; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/357/1018; 639/766/119/2792/4128; 639/766/119/995; 639/766/119/997; Bilayers; Broken symmetry; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Energy dissipation; Ferromagnetism; Graphene; Humanities and Social Sciences; Magnetic moments; Magnetic switching; Magnetism; Magnetization; MATERIALS SCIENCE; multidisciplinary; Quantum Hall effect; Science; Science (multidisciplinary); Substrates; Twisting
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-020-15473-9

Recently, quantum anomalous Hall effect with spontaneous ferromagnetism was observed in twisted bilayer graphenes (TBG) near 3/4 filling. Importantly, it was observed that an extremely small current can switch the direction of the magnetization. This offers the prospect of realizing low energy dissipation magnetic memories. However, the mechanism of the current-driven magnetization switching is poorly understood as the charge currents in graphenes are generally believed to be non-magnetic. In this work, we demonstrate that in TBG, the twisting and substrate induced symmetry breaking allow an out of plane orbital magnetization to be generated by a charge current. Moreover, the large Berry curvatures of the flat bands give the Bloch electrons large orbital magnetic moments so that a small current can generate a large orbital magnetization. We further demonstrate how the charge current can switch the magnetization of the ferromagnetic TBG near 3/4 filling as observed in the experiments. The mechanism of current-driven magnetization switching in twisted bilayer graphene (TBG) is poorly understood. Here, He et al. show that a small current can generate a large orbital magnetization due to symmetry breaking by the twisting and substrate in TBG, leading to a giant orbital magnetoelectric effect.