Magnetic Interaction in Doped 2D Perovskite Cuprates with Nanoscale Inhomogeneity: Lattice Nonlocal Effects vs Superexchange

TL;DR

This paper investigates how nanoscale inhomogeneity and lattice effects influence superexchange interactions in doped 2D cuprates, revealing the role of dynamic stripe structures and symmetry breaking in magnetic properties.

Contribution

It introduces a model linking lattice nonlocal effects and stripe nanostructures to the modulation of superexchange interactions in doped 2D cuprates, highlighting the impact of symmetry breaking.

Findings

Dynamic stripe nanostructures restore homogeneous AFM interactions.

Superexchange interaction decreases exponentially due to dynamic quenching.

Structural features explain experimental phenomena like charge inhomogeneity and symmetry breaking.

Abstract

We have studied the superexchange interaction $J_{ij}$ in doped $2D$ cuprates. The AFM interaction strongly depends on the state of the lattice of a CuO$_2$ layer surrounded by two LaO rock salt layers. In a static $U$ and $D$ stripe nanostructure, the homogeneous AFM interaction is impossible due to the $U/D/U...$ periodic stripe sequence and $T_N=0$. In a dynamic stripe nanostructure, the ideal CuO$_2$ layer with nonlocal effects and the homogeneous AFM interaction are restored. However the interaction $J_{ij}$ decreases by the exponential factor due to partial dynamic quenching. The meaning of the transition from the dynamic to the static cases lies into the spontaneous $\theta$-symmetry breaking with respect to the rotation of all the tilted CuO$_6$ octahedra by an orientation angle $\delta \theta = n \cdot \left( {45^\circ } \right)$ (where $n=1\div4$) in the $U$ and $D$ stripe nanostructure of the CuO$_2$ layer. Moreover, the structural features help to study various experimental data on the charge inhomogeneity, Fermi level pinning in the p type cuprates only and a time reversal symmetry breaking from a unified point of view.