Experimental measurement of emergent composite-fermion dispersion

Establish how the dispersive composite-fermion bands of fractional Chern insulators can be measured experimentally, including how momentum-integrated tunneling spectra or impurity-induced quasiparticle-interference patterns encode the dispersion and geometry of the underlying bands.

Background

The paper constructs composite-fermion wave functions for Jain-state quasiparticles and quasiholes in Aharonov–Casher bands and shows that the resulting charged excitations form dispersive bands despite the exact flatness of the underlying electronic Chern band. In the conventional Landau-level setting, local tunneling spectroscopy can resolve composite-fermion excitation energies, but a dispersive band is expected to broaden the corresponding discrete spectral features into momentum-integrated structures.

The authors identify two possible experimental probes: calculating the full tunneling spectrum in the Aharonov–Casher system and using impurity-induced quasiparticle interference to extract the anyon bandwidth. They further note that scanning-tunneling measurements reveal anisotropic structures near impurities, but the relationship between those structures and the dispersion and geometry of the composite-fermion bands remains to be established.

References

An important remaining question is how the emergent CF dispersion can be measured experimentally. In the Landau-level setting, the peaks in the local tunneling spectrum have been shown to correspond directly to the kinetic energies of CF excitations. A dispersive CF band should broaden these discrete spectral features into momentum-integrated bands, although a quantitative prediction will require calculating the full tunneling spectrum in the AC system. Alternatively, the anyon bandwidth may be extracted from impurity-induced quasiparticle interference, as proposed in Ref.. Recent scanning-tunneling measurements near impurities have also revealed anisotropic spatial structures associated with localized fractional excitations. Establishing how these structures encode the dispersion and geometry of the underlying CF bands is an important direction for future theoretical and experimental work.

— Composite fermions in ideal Chern bands  (2610.01217 - Pu et al., 1 Oct 2026) in Discussion