The annealed positions of ferromagnetic bonds doped into a 2D antiferromagnet

TL;DR

This paper investigates the optimal placement of ferromagnetic bonds in a 2D antiferromagnet, revealing degeneracy in classical states and phase separation when quantum effects are considered, with implications for high-temperature superconductors.

Contribution

It introduces a method to determine the annealed positions of ferromagnetic bonds in a 2D antiferromagnet and explores the effects of quantum fluctuations on ground state configurations.

Findings

Degeneracy of classical ground states with unfrustrated FM bond arrangements.

Quantum fluctuations lift degeneracy, leading to phase-separated states such as stripe patterns.

Relevance to doped cuprate high T_c superconductors with annealed disorder.

Abstract

We determine where a given concentration of ferromagnetic (FM) bonds doped into a square lattice antiferromagnet must go to minimize the system's total magnetic energy. We find (i) an infinite degeneracy of ground--state arrangements of FM bonds that correspond to completely unfrustrated configurations for classical spins, and (ii) this degeneracy is lifted when quantum fluctuations are included, and phase separated ground states, such as periodic arrays of stripes of FM bonds, are found. A discussion of the application of these ideas to doped cuprate high $T_c$ superconductors with annealed disorder is presented.