Orbital-lattice coupling and orbital ordering instability in iron pnictides

TL;DR

This paper investigates orbital-ordering instabilities in iron pnictides caused by orbital-lattice coupling, highlighting their momentum characteristics, doping dependence, and comparison with first-principle electron-phonon coupling calculations.

Contribution

It introduces a detailed analysis of orbital-ordering instabilities in pnictides, emphasizing their incommensurate nature and relation to nematic transitions, with model comparisons and doping effects.

Findings

Incommensurate orbital instabilities are favored over spin-density waves without good interpocket nesting.

Instabilities vary across models and are influenced by doping levels.

Electron-phonon coupling parameters needed for instabilities are consistent with first-principle calculations.

Abstract

Orbital-ordering instability arising due to the intrapocket nesting is investigated for the tight-binding models of pnictides in the presence of orbital-lattice coupling. The incommensurate instabilities with small momentum, which may play an important role in the nematic-ordering transition, vary from model to model besides being more favorable in comparison to the spin-density wave instability in the absence of good interpocket nesting. We also examine the doping dependence of such instabilities. The electron-phonon coupling parameter required to induce them are compared with the first-principle calculations.