The dynamics of a doped hole in cuprates is not controlled by spin fluctuations

TL;DR

This paper demonstrates that the dynamics of a doped hole in cuprates are better understood through models including oxygen orbitals and without relying on spin fluctuations, challenging long-standing beliefs.

Contribution

It shows that explicit oxygen orbital models explain hole dynamics and contradict the idea that spin fluctuations are essential, providing a new perspective on cuprate behavior.

Findings

Hole dispersion matches experiments when modeled on oxygen sublattice

Spin fluctuations are not necessary to explain hole dynamics

Simpler models without spin fluctuations are sufficient for understanding cuprates

Abstract

Twenty seven years after the discovery of high-temperature superconductivity \cite{BedMu}, consensus on its theoretical explanation is still absent. To a good extent, this is due to the difficulty of studying strongly correlated systems near half-filling, needed to understand the behaviour of one or few holes doped into a CuO$_2$ layer. To simplify this task it is customary to replace three-band models \cite{Emery} describing the doping holes as entering the O $2p$ orbitals of these charge-transfer insulators \cite{ZSA} with much simpler one-band Hubbard or $tJ$ models \cite{rev1,rev2}. Here we challenge this approach, showing that not only is the dynamics of a doped hole easier to understand in models that explicitly include the O orbitals, but also that our solution contradicts the long-held belief that the quantum spin fluctuations of the antiferromagnetic (AFM) background play a key role in determining this dynamics. Indeed, we show that the correct, experimentally observed dispersion is generically obtained for a hole moving on the O sublattice, and coupled to a N\'eel lattice of spins without spin fluctuations. This marks a significant conceptual change in our understanding of the relevant phenomenology and opens the way to studying few-holes dynamics without finite-size effect issues \cite{BayoB}, to understand the actual strength of the "magnetic glue".