Magnetic imaging of integer and fractional Chern insulators in tMoTe2

Fractional Chern insulators[1-7] are topologically ordered electronic ground states that may occur at partial filling of a lattice band when time reversal symmetry is broken. Crucially, because they occur in lattice bands rather than Landau levels in case of Fractional Quantum Hall Effect, the energy scale of the Coulomb interaction is set by the lattice spacing rather than the magnetic length, potentially enabling higher energy scales. Here, we use nanoSQUID microscopy to measure the local magnetization of tMoTe₂ as a function of the gate-tuned density and electronic displacement field. We see signatures of robust gapped states with large edge state orbital magnetization at fillings -1 and -⅔, consistent with integer and fractional Chern insulators at these fillings. Samples show a high degree of disorder on the sub-micron scale, likely associated with misalignment of the rotationally faulted layers. We use our local probe to measure the thermodynamic energy locally, revealing significantly larger gap sizes compared to those obtained through optical and transport experiments which average over larger spatial areas.

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