Magneto-elasto-resistivity in FeSe

TL;DR

FeSe exhibits a nematic phase below $T_S$ with no long-range magnetic order and superconductivity below $T_C$. The authors develop a minimal two-band Boltzmann transport model incorporating $x/y$ anisotropy to describe magneto-elasto-resistivity (MER) under uniaxial strain, deriving analytic expressions for MR, Hall effect, and MER in both paramagnetic and nematic regimes. The model reveals two robust features: MER with $B_z$ is field-independent above $T_S$, and MER with in-plane fields shows no magnetic-field dependence at all temperatures, both of which are reproduced without fine-tuning. The results support a multiband description of magneto-elasto-transport in FeSe and likely in other iron-based superconductors, providing a framework that could be extended to extract microscopic scattering and nematic coupling effects.

Abstract

FeSe stands out among iron-based superconductors due to its extended nematic phase without the onset of long-range magnetic order. While strain-dependent electrical resistivity has been extensively explored to probe nematicity, its influence on magneto-transport properties remains less understood. In this work, we present measurements of the magneto-elasto-resistivity in FeSe as a function of temperature and applied magnetic field. Using a minimal multiband Boltzmann model for transport we derive analytical expressions that capture the magnetic behavior of the whole set of experimental data both in the paramagnetic and in the nematic phase. These findings indicate that a multiband framework can robustly describe the magneto-elasto-transport properties in FeSe and arguably in other iron-based superconductors.

Figures (5)

• Figure 1: Temperature dependence of the resistivity of samples S1 and S2 normalized to the values at 280 K. The temperature-derivative is shown in gray and clearly identifies $T_S$ and $T_C$. Inset: Temperature dependence of the resistivity of sample S1 across the superconducting transition at several magnetic fields.
• Figure 2: (a) MR of sample S1 as a function of the applied magnetic field $B$, for different temperatures. (b) Hall resistivity $\rho^{xy}$ vs $B$ of samples S1, measured at different temperatures. Inset: Hall-coefficient $R^H_0$, here derived as the slope of the linear fits in the low-$B$ limit . In both panels (a)-(b), the theoretical fit using Eq.s (\ref{['eq:magneto']}) and (\ref{['eq:RH']}) are shown as solid lines on top of the experimental data (symbols). Fitting parameters are reported in App. \ref{['App:Fit']}.
• Figure 3: (a) ER on sample S1 in out-of-plane fields, from 0 T (black) to 15 T (red), in 3 T-steps shows a systematic increase with increasing field in the orthorhombic phase. The Curie-Weiss-like behavior in the tetragonal phase, including the divergence temperature $T_S$, is field-independent. The theoretical fits using Eq. (\ref{['eq:elasto']}) are shown as dashed lines on top of the experimental data (symbols). Fitting parameters are reported in App. \ref{['App:Fit']}. (b) MER of sample S2 for different magnetic field configurations: zero-field (black), 15 T and $-15$ T in-plane (blue and brown) and 15 T out-of-plane (red). No effect of magnetic fields is visible for in-plane fields.
• Figure 4: Simultaneous fit of the MR and of the Hall resistivity, with the constraint $b_1=a_2$. In both panels (a) and (b), the theoretical fit using Eq.s (\ref{['eq:magneto']}) and (\ref{['eq:RH']}) are shown as solid lines on top of the experimental data (symbols).
• Figure 5: Magnetic-field dependence of the MER extracted form the polynomial fits at various temperatures below $T_S$.