Intrinsic quantized anomalous Hall effect in a moiré heterostructure

• Published in: Science (American Association for the Advancement of Science) Vol. 367; no. 6480; pp. 900 - 903
• Main Authors: Serlin, M, Tschirhart, C L, Polshyn, H, Zhang, Y, Zhu, J, Watanabe, K, Taniguchi, T, Balents, L, Young, A F
• Format: Journal Article
• Language: English
• Published: United States The American Association for the Advancement of Science 21.02.2020; American Association for the Advancement of Science (AAAS)
• Subjects: Boron; Conductance; Electromagnetism; Graphene; Hall effect; Heterostructures; Magnetic fields; Magnetism; Thin films; Topology
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.aay5533

The quantum anomalous Hall (QAH) effect combines topology and magnetism to produce precisely quantized Hall resistance at zero magnetic field. We report the observation of a QAH effect in twisted bilayer graphene aligned to hexagonal boron nitride. The effect is driven by intrinsic strong interactions, which polarize the electrons into a single spin- and valley-resolved moiré miniband with Chern number = 1. In contrast to magnetically doped systems, the measured transport energy gap is larger than the Curie temperature for magnetic ordering, and quantization to within 0.1% of the von Klitzing constant persists to temperatures of several kelvin at zero magnetic field. Electrical currents as small as 1 nanoampere controllably switch the magnetic order between states of opposite polarization, forming an electrically rewritable magnetic memory.