Optical Probes of Fractional Quantum Anomalous Hall Effect in Twisted MoTe2

Near-AA stacked homobilayer moiré MoTe₂ has recently been established as a robust, gate-tunable ferromagnet upon hole doping of the first moiré valence band¹. This behavior arises from the substantial Coulomb exchange interactions of the doped holes in the effective honeycomb lattice, which favors spontaneous spin/valley polarization and a breaking of time reversal symmetry. This, in conjunction with the topologically nontrivial (Chern) bands, and strong correlation effects in the system, has enabled the observation the fractional quantum anomalous Hall effect (FQAHE)  – the zero-field analog to the fractional quantum Hall effect ^2-3. As FQAHE in MoTe₂ has proven quite robust, and the system retains the distinctive optical properties of its constituent TMD monolayers, it is uniquely suited to allow for measurement and manipulation of the topological states using both optical and electrical means. Here, I will discuss our latest experiments leveraging optics to further explore the phase space of the MoTe₂ moiré, as well as to establish additional control knobs for this system. Helically polarized photoluminescence can be controlled by the spontaneous spin/valley polarization of the system. This behavior provides a new approach to investigate the integer and fractional quantum anomalous Hall effects, as well as their tuning by electric field.  In addition, optical probes can provide ease access into the twist angle phase space of the system, the band structure of which has been predicted to change with angle. We hope that, in establishing a link between spin/valley and optical degrees of freedom in an experimental platform with robust, experimentally accessible FQAHE, moiré MoTe₂ can serve as a powerful platform for the study and manipulation of correlated topological effects.