Moiré Zeeman effect in twisted WSe₂/WS₂ heterobilayer

Moiré superlattices introduce an artificial periodicity to the underlying crystalline structures, leading to the emergence of a wide range of novel electronic properties in two-dimensional materials. In particular, the combination of flat moiré minibands and strong Coulomb interactions has resulted in the observation of periodic electronic crystals in twisted layers of transition metal dichalcogenides. These electronic crystals can also give rise to intricate magnetic phenomena. In this study, we present our findings on the moiré Zeeman effect, which originates from local magnetic moments within well-aligned WSe₂/WS₂ heterobilayers. In addition to the previously reported remarkably large g-factor of the WSe₂ A exciton in this heterostructure, we unveil the existence of another high-energy excitonic resonance with an even larger g-factor (five times that of the WSe₂ A exciton). This resonance occurs near the filling condition of one hole per moiré unit cell (i.e., v = -1). Our investigations, supported by continuous model calculations, reveal that these high-energy states are the result of dark excitons being brightened through Umklapp scattering from the moiré mini-Brillouin zone. The observed colossal g-factors, denoted as the moiré Zeeman effect, in these high-energy states can be attributed to the periodic modulation of the local magnetic field when the electron lattice forms a Mott insulating state. These results underscore the potential of moiré superlattices as solid-state platforms for simulating quantum magnetism.