Manifestations of mesoscopic Jahn-Teller real-space pairing and clustering in YBa2Cu3O7-δ -: art. no. 212508

The manifestations of a mesoscopic Jahn-Teller real-space paring interaction in YBa2Cu3O7-delta are described. The interaction of degenerate electronic stets with nonsimetric deformation, which acts on a length scale lsimilar to2-3asimilar toxi(s,) where a is the lattice constant and xi(s) is the superconducting coherence length, gives rise to a mesoscopically inhomogeneous state of coexisting fermions and bosonic pairs that locally break the crystal symmetry. Lattice deformations observed in inelastic neutron scattering and broken-symmetry Raman scattering data are quantitatively examined and appear to confirm the existence of such an interaction. The possibility of pyro and piezoelectricity in YBa2Cu3O7-delta is also predicted, in agreement with observations.