Charge transfer excitations, pair density waves, and superconductivity in moiré materials

The authors demonstrate that in moir\'e transition metal dichalcogenide bilayers strong electron repulsion alone is sufficient to create tightly bound charge-2e bosons called trimers. They consist of two holes bound to a charge-transfer exciton. When the bandwidth of doped holes is small, trimers crystallize into insulating pair density waves. By varying the twist angle to increase the bandwidth, holes and trimers can be tuned to resonance, leading to unconventional superconductivity similar to superfluidity in an ultracold Fermi gas near a Feshbach resonance.