Title: Three-particle mechanism for pairing and superconductivity
Abstract: I will present a new mechanism and an exact theory of electron pairing due to repulsive interaction in doped insulators. When the kinetic energy is small, the dynamics of adjacent electrons on the lattice is strongly correlated. By developing a controlled kinetic energy expansion, I will show that two doped charges can attract and form a bound state, despite and because of the underlying repulsion. This attraction by repulsion is enabled by the virtual excitation of a third electron in the filled band. This three-particle pairing mechanism leads to a variety of novel phenomena at finite doping, including spin-triplet superconductivity, pair density wave, BCS-BEC crossover and Feshbach resonance involving “trimers”. Possible realizations in moire materials, ZrNCl and WTe2 will be discussed.
 V. Crepel and L. Fu, Science Advances 7, eabh2233 (2021)
 V. Crepel and L. Fu, arXiv:2103.12060
 K. Slagle and L. Fu, Phys. Rev. B 102, 235423 (2020)