Semiconductor Moiré materials: Kinetic origin of magnetism in a strongly correlated electron system

Moire superlattices in two dimensional semiconductors have enabled the observation of a wealth of physical phenomena driven by strong electronic correlations, ranging from Mott-Wigner states to fractional Chern insulators. After reviewing electronic and optical properties in this new playground for condensed matter physics, I will describe recent experiments in a frustrated triangular lattice, where we measured magnetic correlations in the vicinity of a Mott-insulator state of electrons. By observing electronic magnetization through the strength of the polarization-selective attractive polaron resonances, we find that when the Mott state is doublon doped, the system exhibits ferromagnetic correlations in agreement with the Nagaoka model. Our observations, which are supported by DMRG calculations, provide direct evidence for itinerant magnetism with a kinetic origin.