Establish the doping range of validity of the magnetic polaron description

Determine the range of hole (impurity) concentrations in doped antiferromagnets over which the magnetic polaron picture remains an adequate description, by quantifying its breakdown with increasing doping and identifying the associated changes in quasiparticle properties and spin correlations.

Background

Magnetic polarons—holes dressed by magnons in antiferromagnets—have been observed and modeled successfully at low doping, but their validity as doping increases is unclear. Antiferromagnetic order is known to be suppressed beyond ~5% hole doping in cuprates, suggesting a transition in the underlying physics.

A precise characterization of the doping window for magnetic polarons would inform the broader understanding of charge dynamics in strongly correlated systems, including possible relevance for unconventional superconductivity.

References

How long the magnetic polaron picture remains adequate when the hole (i.e. impurity) concentration is increased remains presently unclear, although it is widely established that antiferromagnetic order is strongly suppressed beyond approximately 5% hole doping in the cuprates which likely invalidates the linear spin-wave theory underlying Eq.~eqHLinSpnWvetJ.

— Impurities and polarons in bosonic quantum gases: a review on recent progress (2410.09413 - Grusdt et al., 12 Oct 2024) in Subsection "Magnetic polarons" (Section 6: Bose polarons in other settings)