BERRY PHASES, PAIRING SYMMETRY, AND NODELESS D-WAVE STATES IN A STRONGLY CORRELATED POLARON MODEL

We use path integral and exact diagonalization techniques to study the tunneling of dopant-induced hole polarons which are self-localized by electron-phonon coupling in a two-dimensional anti-ferromagnet, Their low-energy dynamics is found to be dominated by 2nd and 3rd neighbor hopping processes which carry a (-1) Berry phase factor and lead to no n-s-wave hole pairing symmetries, including possible nodeless d(x2-y2) pair wavefunctions. The nodeless The polarons obey effective spin-1/2 -fermion quasi-particle statistics. d(x2-y2)-wave pairing state can ex hibit a transition from gapless to fully gapped behavior in its quasi- particle excitation spectrum, without change of pairing symmetry.