Berry phases, pairing symmetry, and nodelessd-wave states in a strongly correlated polaron model

Abstract

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 non-s-wave hole pairing symmetries, including possiblenodeless\(d_{x^2 - y^2 } \) pair wavefunctions. The polarons obey effective spin-1/2-fermion quasi-particle statistics. The nodeless\(d_{x^2 - y^2 } \)-wave pairing state can exhibit a transition from gapless to fully gapped behavior in its quasi-particle excitation spectrum, without change of pairing symmetry.