Nematic state stabilized by off-site Coulomb interaction in iron-based superconductors

TL;DR

This study shows that off-site Coulomb interactions can stabilize nematic states in iron-based superconductors, with properties that diminish upon electron doping, aligning with experimental observations.

Contribution

It reveals the crucial role of off-site Coulomb interaction in stabilizing nematic states, a factor previously neglected in models of iron-based superconductors.

Findings

Nematic state stabilized by off-site Coulomb interaction.

Anisotropic properties decrease with electron doping.

Results align with optical and ARPES experimental data.

Abstract

Using a variational Monte Carlo method, we investigate the nematic state in iron-base superconductors based on a three-band Hubbard model. Our results demonstrate that the nematic state, formed by introducing an anisotropic hopping order into the projected wave function, can arise in the underdoped regime when a realistic off-site Coulomb interaction $V$ is considered. {\color {red} We demonstrate that the off-site Coulomb interaction $V$, which is neglected so far in the analysis of iron-base superconductors, make a dominant contribution to the stabilization of nematic state. We calculate the doping dependencies of the anisotropic properties such as the unequal occupation of $d_{xz}$ and $d_{yz}$ orbitals, anisotropies of kinetic energy and spin correlations, and show that they are all suppressed upon electron doping, which are consistent with the intrinsic anisotropies observed by optical spectrum measurement and ARPES experiments.