In-plane electronic anisotropy revealed by interlayer resistivity measurements on the iron-based superconductor parent compound CaFeAsF

TL;DR

This study reveals the in-plane electronic anisotropy in CaFeAsF through interlayer resistivity measurements under magnetic fields, providing insights into nematicity's role in iron-based superconductors.

Contribution

It introduces a novel measurement approach using interlayer resistivity under magnetic fields to probe electronic nematicity in iron-based superconductors.

Findings

Interlayer resistivity is larger in the longitudinal magnetic field configuration.

Resistivity shows a coherence peak under in-plane magnetic fields.

Magnetoresistance varies significantly with in-plane magnetic field direction.

Abstract

Both cuprates and iron-based superconductors demonstrate nematicity, defined as the spontaneous breaking of rotational symmetry in electron systems. The nematic state can play a role in the high-transition-temperature superconductivity of these compounds. However, the microscopic mechanism responsible for the transport anisotropy in iron-based compounds remains debatable. Here, we investigate the electronic anisotropy of CaFeAsF by measuring its interlayer resistivity under magnetic fields with varying field directions. Counterintuitively, the interlayer resistivity was larger in the longitudinal configuration ($B \parallel I \parallel c$) than in the transverse one ($B \perp I \parallel c$). The interlayer resistivity exhibited a so-called coherence peak under in-plane fields and was highly anisotropic with respect to the in-plane field direction. At $T$ = 4 K and $B$ = 14 T, the magnetoresistance $\Delta\rho/\rho_0$ was seven times larger in the $B \parallel b_o$ than in the $B \parallel a_o$ configuration. Our theoretical calculations of the conductivity based on the first-principles electronic band structure qualitatively reproduced the above observations but underestimated the magnitudes of the observed features. The proposed methodology can be a powerful tool for probing the nematic electronic state in various materials.