Non-analytic spin susceptibility of a nested Fermi liquid: the case of Fe-based pnictides

TL;DR

This paper explains the linear temperature dependence of spin susceptibility in Fe-based pnictides as a non-analytic effect in a nested two-dimensional Fermi liquid, linking it to SDW fluctuations and experimental observations.

Contribution

It introduces a theoretical model connecting SDW fluctuations to the linear T dependence of susceptibility in ferropnictides, explaining experimental results.

Findings

Linear T dependence of susceptibility explained by non-analytic Fermi liquid behavior.

Prefactor of T term related to SDW amplitude between nested pockets.

Quantitative agreement with experimental measurements.

Abstract

We propose an explanation of the peculiar linear temperature dependence of the uniform spin susceptibility $\chi(T)$ in ferropnictides. We argue that the linear in $T$ term appears due to non-analytic temperature dependence of $\chi(T)$ in a two-dimensional Fermi liquid. We show that the prefactor of the $T$ term is expressed via the square of the spin-density-wave (SDW) amplitude connecting nested hole and electron pockets. Due to an incipient SDW instability, this amplitude is large, which, along with a small value of the Fermi energy, makes the $T$ dependence of $\chi(T)$ strong. We demonstrate that this mechanism is in quantitative agreement with the experiment.