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Intrinsic quantized anomalous Hall effect in a moiré heterostructure.

M Serlin1, C L Tschirhart1, H Polshyn1

  • 1Department of Physics, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.

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This summary is machine-generated.

Researchers observed the quantum anomalous Hall (QAH) effect in twisted bilayer graphene, enabling precise Hall resistance quantization without magnetic fields. This breakthrough offers potential for rewritable magnetic memory applications.

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Area of Science:

  • Condensed matter physics
  • Materials science
  • Quantum phenomena

Background:

  • The quantum anomalous Hall (QAH) effect is a topological phenomenon combining topology and magnetism, resulting in quantized Hall resistance at zero magnetic field.
  • Previous studies often relied on magnetically doped systems, which have limitations in stability and energy gap characteristics.

Purpose of the Study:

  • To report the observation of the QAH effect in a novel material system: twisted bilayer graphene aligned to hexagonal boron nitride.
  • To investigate the underlying mechanisms and characteristics of the QAH effect in this system, particularly focusing on intrinsic interactions and magnetic ordering.

Main Methods:

  • Fabrication of twisted bilayer graphene precisely aligned with hexagonal boron nitride.
  • Transport measurements to observe quantized Hall resistance at zero magnetic field.
  • Characterization of the material's magnetic properties and energy gap in relation to temperature and magnetic ordering.

Main Results:

  • Observation of the QAH effect driven by intrinsic strong interactions, polarizing electrons into a single spin- and valley-resolved moiré miniband with Chern number C = 1.
  • The measured transport energy gap exceeds the Curie temperature, indicating robust magnetic ordering.
  • Precise quantization of Hall resistance (within 0.1% of the von Klitzing constant) persists to several Kelvin at zero magnetic field.
  • Electrical currents as low as 1 nanoampere can controllably switch the magnetic order, enabling rewritable magnetic memory.

Conclusions:

  • Twisted bilayer graphene aligned to hexagonal boron nitride is a viable platform for realizing the quantum anomalous Hall effect.
  • The observed effect is robust, with a significant energy gap and persistent quantization at higher temperatures and zero magnetic field.
  • The material's ability to be electrically switched opens possibilities for developing novel, high-density, and low-power magnetic memory devices.