A time-domain view of fractional Chern insulators in twisted MoTe₂ bilayers

The twisted Mote₂ moiré system has emerged as an excellent platform for exploring a broad range of two-dimensional (2D) topological quantum phases, as exemplified by the landmark discovery of the fractional quantum anomalous Hall effect at fractional fillings -2/3 and -3/5. This success has motivated the search for a variety of topological quantum matter in this system. Recently, we demonstrated pump-probe spectroscopy as the most sensitive approach for detecting many-body correlations and potential hidden quantum phases. In this technique, a pump pulse disrupts the many-body correlation and the resulting increase in the dielectric constant is monitored by exciton sensing. This approach has revealed many fractional phases that previously evaded detection in transport and static optical measurements. Here, we take the approach one step further by leveraging the valley-selective optical excitation in transition metal dichalcogenides (TMDs) using circularly polarized light. We show our preliminary findings of the rich repertoire of fractional states up to ν=-3, with cases of time-reversal (TR) invariance and spontaneous TR-symmetry breaking. These findings provide experimental verification of various theoretical predictions of fractional Chern insulators in this system.