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

TL;DR

This paper investigates the interactions of doped holes in cuprates, revealing how quasiparticles like Zhang-Rice singlets and polarons interact and may contribute to superconductivity through quantum lattice fluctuations.

Contribution

It provides ab initio calculations showing the interplay of quasiparticles and lattice vibrations, proposing a mechanism for superconductivity involving quantum lattice fluctuations.

Findings

Repulsive interaction between Zhang-Rice singlets and polarons

Long-range Coulomb interactions influence polaron energy barriers

Quantum lattice fluctuations may facilitate superconductivity

Abstract

In-plane, inter-carrier 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) CuO4 singlet states and Jahn-Teller polarons. The interaction between these quasiparticles is repulsive. At doping levels 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, multi-well energy landscape. We suggest that the coherent, superconducting quantum state is the result of such coherent quantum lattice fluctuations involving the in-plane O ions. Our findings appear to support models where the superconductivity is related to a lowering of the in-plane kinetic energy.