Hb. Schuttler et al., BERRY PHASES, PAIRING SYMMETRY, AND NODELESS D-WAVE STATES IN A STRONGLY CORRELATED POLARON MODEL, Journal of superconductivity, 8(5), 1995, pp. 555-558
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.