Coexistence of orbital and quantum critical magnetoresistance in FeSe1−xSx

S Licciardello,M Čulo,J Ayres,B Bryant,V Nagarajan,J Buhot,J G Analytis,T Shibauchi,N Maksimovic,Y Matsuda,N E Hussey,S Kasahara

doi:10.1103/physrevresearch.1.023011

Abstract

The recent discovery of a non-magnetic nematic quantum critical point (QCP) in the iron chalcogenide family FeSe$_{1-x}$S$_{x}$ has raised the prospect of investigating, in isolation, the role of nematicity on the electronic properties of correlated metals. Here we report a detailed study of the normal state transverse magnetoresistance (MR) in FeSe$_{1-x}$S$_{x}$ for a series of S concentrations spanning the nematic QCP. For all temperatures and \textit{x}-values studied, the MR can be decomposed into two distinct components: one that varies quadratically in magnetic field strength $\mu_{0}\textit{H}$ and one that follows precisely the quadrature scaling form recently reported in metals at or close to a QCP and characterized by a \textit{H}-linear MR over an extended field range. The two components evolve systematically with both temperature and S-substitution in a manner that is determined by their proximity to the nematic QCP. This study thus reveals unambiguously the coexistence of two independent charge sectors in a quantum critical system. Moreover, the quantum critical component of the MR is found to be less sensitive to disorder than the quadratic (orbital) MR, suggesting that detection of the latter in previous MR studies of metals near a QCP may have been obscured.

Highlights

Many strongly interacting electron systems lie in close proximity to a quantum critical point (QCP), realized by suppressing a finite temperature ordering transition to zero temperature via some nonthermal tuning parameter [1]
The observation of QC scaling in the MR response of the second crystal reveals that while the orbital component is effectively quenched with increasing impurity scattering (a 5-fold increase in the residual resistivity would correspond to a 25-fold decrease in the orbital MR at low T ), the QC component remarkably survives
We have carried out a systematic study of the transverse MR in a series of FeSe1-xSx single crystals in high magnetic fields up to 38 T for S concentrations that span the nematic QCP

Summary

Introduction

Many strongly interacting electron systems lie in close proximity to a quantum critical point (QCP), realized by suppressing a finite temperature ordering transition to zero temperature via some nonthermal tuning parameter [1]. Metallic quantum critical systems exhibit anomalous transport and thermodynamic properties, including (but not restricted to) a T-linear resistivity at low temperatures [2,3,4] and a logarithmic divergence of the electronic specific heat [5]. A new feature of metallic quantum criticality was discovered in the transverse magnetoresistance (whereby the magnetic field is applied perpendicular to the current) in the iron pnictide compound BaFe2(As1-xPx ) (Ba122) near its antiferromagnetic QCP [6].

Methods

Results

Discussion

Conclusion