Binding of Holes to Magnetic Impurities in a Strongly Correlated System

TL;DR

This study investigates how magnetic impurities in a strongly correlated 2D electron system influence hole binding, revealing bound states with various symmetries and their spectral signatures using exact diagonalization.

Contribution

It demonstrates the formation of bound states between holes and magnetic impurities in the t--J model, highlighting the dependence on impurity coupling and symmetry characteristics.

Findings

Bound states form with different symmetries depending on impurity coupling.

Maximum binding energy occurs at decoupled impurity (vacancy).

Multiple spectral peaks indicate various bound state symmetries.

Abstract

The effect of a magnetic (S=1/2) impurity coupled to a 2D system of correlated electrons (described by the t--J model) is studied by exact diagonalisations. It is found that, if the exchange coupling of the impurity with the neighboring spins is ferromagnetic or weakly antiferromagnetic, an extra hole can form bound states of different spatial symmetries with the impurity extending to a few lattice spacings. The binding energy is maximum when the impurity is completely decoupled (vacancy) and vanishes for an antiferromagnetic coupling exceeding $\sim 0.3 J$. Several peaks appear in the single hole spectral function below the lower edge of the quasiparticle band as signatures of the d-, s- and p-wave boundstates.