Hidden states and dynamics of fractional fillings in twisted MoTe2 bilayers

The fractional quantum anomalous Hall (FQAH) effect was recently discovered in twisted MoTe2 (tMoTe2) bilayers1–4. Experiments so far have revealed Chern insulators from hole doping at ν = −1, −2/3, −3/5 and −4/7 (per moiré unit cell)1–6. In parallel, theories predict that, between v = −1 and −3, there exist exotic quantum phases7–15, such as the coveted fractional topological insulators, fractional quantum spin Hall (FQSH) states and non-Abelian fractional states. Here we use transient optical spectroscopy16,17 on tMoTe2 to reveal nearly 20 hidden states at fractional fillings that are absent in static optical sensing or transport measurements. A pump pulse selectively excites charge across the correlated or pseudogaps, leading to the disordering (melting) of correlated states18. A probe pulse detects the subsequent melting and recovery dynamics by means of exciton and trion sensing1,3,19–21. Besides the known states, we observe further fractional fillings between ν = 0 and −1 and a large number of states on the electron doping side (ν > 0). Most importantly, we observe new states at fractional fillings of the Chern bands at ν = −4/3, −3/2, −5/3, −7/3, −5/2 and −8/3. These states are potential candidates for the predicted exotic topological phases7–15. Moreover, we show that melting of correlated states occurs on two distinct timescales, 2–4 ps and 180–270 ps, attributed to electronic and phonon mechanisms, respectively. We discuss the differing dynamics of the electron-doped and hole-doped states from the distinct moiré conduction and valence bands.