2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/16951Based on the Hubbard model description of the doped Mott insulator, we prove that there must exist a spinless collective excitation of charge $2e$ and of energy $U-2μ$ peaked at momentum $(π/a,π/a)$ in the non-superconducting state due to doping. Such a collective excitation arises from the electron pair correlation. Its existence is related to the breakdown of an approximate SU(2) particle-hole symmetry, from which an effective field theory of the new excitations is constructed.4 pagesStrongly Correlated ElectronsSuperconductivitytext