Visualizing band selective enhancement of quasiparticle lifetime in a metallic ferromagnet

Na Hyun Jo,S L Bud’Ko,Benjamin Schrunk,P C Canfield,Adam Kaminski,Lin-Lin Wang,Yun Wu,Thaís V Trevisan,Brinda Kuthanazhi,P P Orth,Kyungchan Lee

doi:10.1038/s41467-021-27277-6

Abstract

Electrons navigate more easily in a background of ordered magnetic moments than around randomly oriented ones. This fundamental quantum mechanical principle is due to their Bloch wave nature and also underlies ballistic electronic motion in a perfect crystal. As a result, a paramagnetic metal that develops ferromagnetic order often experiences a sharp drop in the resistivity. Despite the universality of this phenomenon, a direct observation of the impact of ferromagnetic order on the electronic quasiparticles in a magnetic metal is still lacking. Here we demonstrate that quasiparticles experience a significant enhancement of their lifetime in the ferromagnetic state of the low-density magnetic semimetal EuCd2As2, but this occurs only in selected bands and specific energy ranges. This is a direct consequence of the magnetically induced band splitting and the multi-orbital nature of the material. Our detailed study allows to disentangle different electronic scattering mechanisms due to non-magnetic disorder and magnon exchange. Such high momentum and energy dependence quasiparticle lifetime enhancement can lead to spin selective transport and potential spintronic applications.

Highlights

Electrons navigate more in a background of ordered magnetic moments than around randomly oriented ones
The observed upturn above the transition temperature is associated with magnetic fluctuations
As we show in our theory modeling below, the increased lifetime of the inner band can be associated with a reduced impurity scattering rate of majority carriers due to phase space constraints

Summary

Introduction

Electrons navigate more in a background of ordered magnetic moments than around randomly oriented ones. For ferromagnetic (FM) order the periodicity remains unchanged, but instead the bands experience a FM exchange splitting, leading to different FSs for majority and minority carriers The effect of such band splitting on the properties of itinerant carriers and the impact of their coupling to fluctuations of the magnetic moments are important open questions that we address here. We show that its electronic quasiparticles experience a significant lifetime enhancement in certain bands and energy ranges We associate this effect with the emergence of different impurity and magnetic scattering rates for majority and minority carriers due to distinct phase spaces of the respective scattering processes.

Methods

Results

Conclusion