EQuAL Seminar: Evgeny Redekop

"Direct Magnetic Imaging of Fractional Chern Insulators in Twisted MoTe2 with a Superconducting Sensor"

Fractional Chern insulators 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 electric displacement field. We see robust gapped states with large edge state orbital magnetization at fillings of -1, -2/3, -3/5, -4/7 and -5/9 consistent with integer and fractional Chern insulators. Samples show a high degree of disorder on the sub-micron scale. 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.