Nonlocal interactions in doped cuprates: Correlated motion of Zhang-Rice polarons

Abstract

Intercarrier correlations in hole doped cuprates are investigated by ab initio multiconfiguration calculations. The dressed carriers display features that are reminiscent of both Zhang-Rice (ZR) $\mathrm{Cu}{\mathrm{O}}_{4}$ states and Jahn-Teller polarons. The interaction between these quasiparticles is repulsive. At dopings that are high enough, the interplay between long-range unscreened Coulomb interactions and long-range phase coherence among the O-ion half-breathing vibrations on the ZR plaquettes may lead to a strong reduction of the effective adiabatic energy barrier associated to each polaronic state. Tunneling effects cannot be neglected for a relatively flat, multiwell energy landscape. We suggest that the coherent, superconducting quantum state is the result of such coherent quantum lattice fluctuations involving in-plane O ions. Our findings appear to support phenomenological models where the superconductivity is related to a lowering of the in-plane kinetic energy.