New Developments in Fractional Quantum Anomalous Hall Effect

The interplay between spontaneous symmetry breaking and topology can result in exotic quantum states of matter. A celebrated example is the quantum anomalous Hall (QAH) effect, which exhibits an integer quantum Hall effect at zero magnetic field due to topologically nontrivial bands and intrinsic magnetism. In the presence of strong electron-electron interactions, fractional-QAH (FQAH) effect at zero magnetic field can emerge, which is the lattice analog of the fractional quantum Hall effect without Landau level formation. In this talk, I will first discuss the experimental observation of the FQAH effect in twisted MoTe₂ bilayer, using combined magneto-optical and magneto-transport measurements. Then I will present new developments in this direction, including the observation of abundant Jain sequence of fractional Chern insulator states, as well as results on improved samples where quantized fractional plateaus with vanishing longitudinal resistance are observed. Direct observation of the FQAH and associated effects paves the way for researching charge fractionalization and anyonic statistics at zero magnetic field.