Related Experiment Video
Updated: Jul 17, 2026
11:42
Fabrication of Gate-tunable Graphene Devices for Scanning Tunneling Microscopy Studies with Coulomb Impurities
Published on: July 24, 2015
Fractional high-Chern insulator in twisted rhombohedral graphene
Zexu Li1, Wenxuan Wang2, Fajie Wang1
1International Center for Quantum Materials, School of Physics, Peking University, Beijing, China.
Nature
|July 15, 2026
Summary
Researchers explored moiré flat-band systems, discovering novel quantum anomalous Hall insulators and an exotic fractional Chern insulator with a Chern number of 7/3. This opens new avenues for studying anyons and fractionally charged excitations without magnetic fields.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Physics
Background:
- Fractional Chern insulators enable exploration of exotic phenomena like fractional charge and anyonic statistics.
- A key question is whether lattice systems can host novel states beyond traditional fractional quantum Hall systems.
Purpose of the Study:
- Investigate moiré flat-band systems for new quantum states.
- Discover novel topological phases and fractional Chern insulators.
Main Methods:
- Utilized moiré flat-band systems composed of Bernal bilayer graphene and rhombohedral tetralayer graphene.
- Analyzed quantum anomalous Hall insulators and fractional Chern insulators at specific moiré filling factors.
Main Results:
- Discovered quantum anomalous Hall insulators with Chern numbers ranging from |C|=1 to |C|=7 at filling factor v=1 and around v=3.
- Observed an unprecedented fractional Chern insulator with C=7/3 around v=2/3, extending beyond known theories.
Conclusions:
- The findings expand the understanding of fractionally charged excitations beyond the Landau-level framework.
- Moiré flat-band systems provide a promising platform for exploring anyons and novel topological states.
Related Concept Videos
01:07Radicals: Electronic Structure and Geometry
This lesson delves into the geometry of a radical, which is influenced by the electronic structure of the molecule. The principle is similar to that of a lone pair, where the unpaired electron influences the geometry at the radical center.
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
01:26Imperfections in Crystal Structure: Stoichiometric Point Defects
Schottky defects arise when some lattice points in a crystal, such as those in NaCl, remain unoccupied, creating lattice vacancies without disturbing the overall electrical neutrality of the crystal. This defect is common in ionic crystals where the positive and negative ions are similar in size, as seen in sodium chloride and cesium chloride. The presence of Schottky defects enables the crystal to conduct electricity to a small extent through an ionic mechanism. Electric fields cause nearby...
02:37Metallic Solids
Metallic solids such as crystals of copper, aluminum, and iron are formed by metal atoms. The structure of metallic crystals is often described as a uniform distribution of atomic nuclei within a “sea” of delocalized electrons. The atoms within such a metallic solid are held together by a unique force known as metallic bonding that gives rise to many useful and varied bulk properties.
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and malleability. Many...
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and malleability. Many...
03:24Hybridization of Atomic Orbitals I
The mathematical expression known as the wave function, ψ, contains information about each orbital and the wavelike properties of electrons in an isolated atom. When atoms are bound together in a molecule, the wave functions combine to produce new mathematical descriptions that have different shapes. This process of combining the wave functions for atomic orbitals is called hybridization and is mathematically accomplished by the linear combination of atomic orbitals. The new orbitals that...
04:01VSEPR Theory and the Effect of Lone Pairs
Effect of Lone Pairs of Electrons on Molecule Geometry