Fate of doped carriers in silver fluoride cuprate analogues

TL;DR

This study uses ab initio calculations to explore doping strategies in AgF₂, revealing potential pathways to metallicity and high-temperature superconductivity, with implications for developing new unconventional superconductors.

Contribution

The paper demonstrates that doping AgF₂ can lead to metallization and suggests flat allotropes may enhance this effect, offering new avenues for superconductivity research.

Findings

Electron doping causes strongly self-trapped states (polarons) due to narrow Hubbard band.

Hole doping shows moderate polaron formation, indicating possible metallicity at high doping levels.

Flat AgF₂ allotropes have excellent potential to become metallic and support superconductivity.

Abstract

AgF$_2$ is a correlated charge-transfer insulator with properties remarkably similar to insulating cuprates which have raised hope that it may lead to a new family of unconventional superconductors upon doping. We use ab initio computations to study doping strategies leading to metallization. Because the upper Hubbard band is very narrow electron doping leads to undesired strongly self-trapped states (polarons). For the hole-doped case, polaron tendency is stronger than for cuprates but still moderate enough to expect that heavily doped compounds may become metallic. Since the strong electron lattice coupling originates in the strong buckling we study also an hypothetically flat allotrope and show that it has excellent prospect to become metallic. We compare the AgF2 behavior with that for the hole-doped conventional cuprate La$_2$CuO$_4$ and electron-doped Nd$_2$CuO$_4$. Our results show a clear path to achieve high temperature superconductivity in silver fluorides.