Doping a correlated band insulator: A new route to half metallic behaviour

TL;DR

This paper shows that introducing Coulomb interactions in a doped band insulator can induce a half-metallic state, offering a new pathway for spintronics applications based on correlated electron systems.

Contribution

It reveals that Coulomb interactions can induce half-metallicity in doped insulators, a novel mechanism demonstrated through dynamical mean field theory.

Findings

Turning on Coulomb U causes a transition to half-metallic ferrimagnetism upon doping.

A first order transition occurs between paramagnetic band insulator and antiferromagnetic Mott insulator.

Half-metallic behavior persists over a wide doping and interaction range.

Abstract

We demonstrate in a simple model the surprising result that turning on an on-site Coulomb interaction U in a doped band insulator leads to the formation of a half-metallic state. In the undoped system, we show that increasing U leads to a first order transition between a paramagnetic, band insulator and an antiferomagnetic Mott insulator at a finite value U_{AF}. Upon doping, the system exhibits half metallic ferrimagnetism over a wide range of doping and interaction strengths on either side of U_{AF}. Our results, based on dynamical mean field theory, suggest a novel route to half-metallic behavior and provide motivation for experiments on new materials for spintronics.