Spin-orbital polarons in electron doped copper oxides

TL;DR

This paper reveals the formation of spin-orbital polarons in electron-doped copper oxides, where electrons become self-trapped in filamentary channels due to oxygen orbital polarization, influencing magnetic and superconducting properties.

Contribution

It introduces the concept of spin-orbital polarons with a novel self-trapping mechanism in one-dimensional channels, differing from previous interpretations.

Findings

Formation of filamentary spin-orbital polarons in electron-doped copper oxides

Evolution of filament web affecting antiferromagnetic correlations

Quantum phase transitions induced by doping levels

Abstract

Present work demonstrates the formation of spin-orbital polarons in electron doped copper oxides, that arise due to doping-induced polarisation of the oxygen orbitals in the CuO$_2$ planes. The concept of such polarons is fundamentally different from previous interpretations. The novel aspect of spin-orbit polarons is best described by electrons becoming self-trapped in one-dimensional channels created by polarisation of the oxygen orbitals. The one-dimensional channels form elongated filaments with two possible orientations, along the diagonals of the elementary CuO$_2$ square plaquette. As the density of doped electrons increases multiple filaments are formed. These may condense into a single percollating filamentary phase. Alternatively, the filaments may cross perpendicularly to create an interconnected conducting quasi-one-dimensional web. At low electron doping the antiferromagnetic (AFM) state and the polaron web coexist. As the doping is increased the web of filaments modifies and transforms the AFM correlations leading to a series of quantum phase transitions - which affect the normal and superconducting state properties.