New Material Joins Moiré Family
Since 2018, condensed-matter physicists have been fascinated by so-called moiré materials, stacks of atomically thin crystalline layers that are slightly twisted or otherwise misaligned relative to each other. These small misalignments change how electrons move and interact, potentially inducing superconductivity and other unusual electronic effects. Now Yan Sun at the University of Paris-Saclay and her colleagues have shown how the phenomena accessible in moiré materials can be enriched by adding lead iodide, a layered semiconductor with an intrinsically strong coupling between electron spin and orbital motion [1].
The team fabricated a moiré material in which four layers of lead iodide were placed under a layer of hexagonal boron nitride and a layer of graphene, with carefully selected twist angles between each component. The researchers cooled the material to an ultralow temperature and then applied a voltage and a strong magnetic field. They found that, for a certain range of voltages, the material’s electrical conductance was equal to two-thirds of the fundamental conductance quantum. This striking feature points to the formation of unconventional, strongly correlated electronic states.
Sun and her colleagues also found that an electric current could travel through the material with almost no energy loss at the so-called charge-neutrality point, the operating condition for which there are equal numbers of positive and negative charge carriers. Under this condition, the material’s longitudinal resistance became zero in the presence of a strong magnetic field, indicating that the electrons moved without scattering. The researchers suggest that this ballistic motion was achieved through special moiré-mediated channels, made possible by the strong spin–orbit coupling of the material’s lead iodide layers.
–Ryan Wilkinson
Ryan Wilkinson is a Corresponding Editor for Physics Magazine based in Durham, UK.
References
- Y. Sun et al., “Chern junctions in moiré-patterned graphene/PbI2,” Phys. Rev. B 113, 155425 (2026).