In-plane anisotropy of transport coefficients in the electronic nematic states: Universal origin of the nematicity in Fe-based superconductors

Abstract

The origin of the electronic nematicity and its remarkable material-dependence are famous longstanding unsolved issues in Fe-based superconductors. To attack these issues, we focus on the in-plane anisotropy of the resistivity: In the nematic state in FeSe, the relation $ρ_x>ρ_y$ holds, where $ρ_{x(y)}$ is the resistivity along the longer (shorter) Fe-Fe axis. In contrast, the opposite anisotropy $ρ_x<ρ_y$ is realized in other undoped Fe-based superconductors. Such nontrivial material dependence is naturally explained in terms of the strongly orbital-dependent inelastic quasiparticle scattering realized in the orbital-ordered state. The opposite anisotropy between FeSe ($ρ_x>ρ_y$) and other undoped compounds ($ρ_x<ρ_y$) reflects the difference in the number of hole-pockets. We also explain the large in-plane anisotropy of the thermoelectric power in the nematic state.

10 pages, 10 figures