Negative $c$-axis longitudinal magnetoresistance in FeSe

TL;DR

This paper reports the discovery of significant negative c-axis longitudinal magnetoresistance in FeSe below the structural transition, linked to spin fluctuation scattering, revealing complex spin-orbital interactions in its nematic phase.

Contribution

It provides the first observation of negative c-axis longitudinal magnetoresistance in FeSe and connects it to spin fluctuation effects in the nematic phase.

Findings

Negative magnetoresistance of about 15% at 10 K and 16 T along c-axis.

Magnetoresistance behavior differs between transverse and longitudinal configurations.

Spin fluctuations influence electron scattering in the nematic phase.

Abstract

Below the structural transition occurring at $T_s=90$\,K, FeSe exhibits positive transverse magnetoresistance when the current is applied parallel to the $ab$-plane. In this study, we show that, in contrast, when both the magnetic field and the current are aligned along the $c$-axis, the magnetotransport changes significantly. In this configuration, FeSe develops a sizable negative longitudinal magnetoresistance ($\sim$15\% at $T$=10\,K and $\mu_0H$=16\,T) in the nematic phase. We attribute this finding to the effect of the applied magnetic field on the scattering from spin fluctuations. Our observations reflect the intricate interplay between spin and orbital degrees of freedom in the nematic phase of FeSe.