Nematicity driven by hybridization in iron-based superconductors

TL;DR

This paper proposes a theoretical model where hybridization between localized and itinerant electrons in iron-based superconductors leads to nematic order, explaining observed nematicity in these materials.

Contribution

It introduces a new effective model demonstrating how excitonic condensation can spontaneously break lattice symmetry, causing nematicity in iron-based superconductors.

Findings

Hybridization induces excitonic order in the model.

Spontaneous C_4 symmetry breaking leads to nematicity.

The mechanism explains nematic tendencies in iron-based compounds.

Abstract

In this paper we study an effective model for the normal state of iron-based superconductors. It has separate, but interacting itinerant and localized degrees of freedom, originating from the d_xz and d_yz, and from d_xy iron orbitals respectively. At low temperatures, below a mean-field phase transition, these different states condense together in an excitonic order parameter. We show that at even lower temperature, after another phase transition, this ordered state can spontaneously break the C_4 lattice symmetry and become nematic. We propose this mechanism as an explanation of the tendency towards nematicity observed in several iron-based compounds.