Non-Fermi liquid transport in the vicinity of nematic quantum critical point of FeSe$_{1-x}$S$_x$ superconductor

TL;DR

This study investigates non-Fermi liquid behavior near a nematic quantum critical point in FeSe$_{1-x}$S$_x$, revealing anomalous transport properties that resemble those in other unconventional superconductors, indicating nematic fluctuations cause Fermi liquid breakdown.

Contribution

It provides experimental evidence of non-Fermi liquid transport linked to nematic quantum criticality in FeSe$_{1-x}$S$_x$, highlighting the role of ${f q} ightarrow 0$ nematic fluctuations.

Findings

Linear-in-temperature resistivity close to Planckian limit

Hall angle varies as T^2 near criticality

Magnetoresistance scales with Hall angle squared

Abstract

Non-Fermi liquids are strange metals whose physical properties deviate qualitatively from those of conventional metals due to strong quantum fluctuations. In this paper, we report transport measurements on the FeSe$_{1-x}$S$_x$ superconductor, which has a quantum critical point of a nematic order without accompanying antiferromagnetism. We find that in addition to a linear-in-temperature resistivity $\rho_{xx}\propto T$, which is close to the Planckian limit, the Hall angle varies as $\cot \theta_{\rm H} \propto T^2$ and the low-field magnetoresistance is well scaled as $\Delta\rho_{xx}/\rho_{xx}\propto \tan^2 \theta_{\rm H}$ in the vicinity of the nematic quantum critical point. This set of anomalous charge transport properties shows striking resemblance with those reported in cuprate, iron-pnictide and heavy fermion superconductors, demonstrating that the critical fluctuations of a nematic order with ${\bf q} \approx 0$ can also lead to a breakdown of the Fermi liquid description.