Impurity effects and ferromagnetism in excitonic insulators

TL;DR

This paper investigates how impurities affect the magnetic and electronic properties of excitonic insulators, revealing impurity-induced bound states and their implications for ferromagnetism and symmetry detection.

Contribution

It provides a detailed analysis of impurity effects on spin singlet and triplet excitonic insulators, including bound state energies and pair-breaking effects, offering new insights into their magnetic behavior.

Findings

Impurities create bound states that can identify excitonic insulator symmetry.

Nonmagnetic impurities have similar pair-breaking effects in both singlet and triplet cases.

Magnetic impurities weaken pair-breaking in triplet excitonic insulators, influencing ferromagnetism.

Abstract

Both nonmagnetic and magnetic impurity effects in spin singlet and triplet excitonic insulators were investigated. The bound state energies caused by single impurity were given. The different compositions of the bound states can be used to detect the symmetry of the excitonic insulators. In finite concentration problems, nonmagnetic impurities showed same pair-breaking effect in singlet and triplet excitonic insulators while magnetic impurities showed weaker pair-breaking effect in triplet excitonic insulators than in singlet ones. The pair-breaking effects suppressed the ferromagnetic range via doping and gave a natural explaination for experimental results.