FeAs$_2$ formation and electronic nematic ordering: Analysis in terms of structural transformations

TL;DR

This study combines computational analysis and symmetry considerations to understand FeAs₂'s structure and electronic nematic order, revealing the interplay between lattice and electron degrees of freedom that influences its properties.

Contribution

It provides a detailed analysis of FeAs₂'s structural formation and electronic nematic ordering using DFT and symmetry constraints, highlighting the role of orbital localization and charge redistribution.

Findings

FeAs₂ exhibits nematic-like electronic ordering linked to Fe 3d orbitals.

Structural analysis shows a preference for orthorhombic Pnnm lattice.

Charge redistribution enhances electronic polarizability and charge transfer effects.

Abstract

By combining DFT-based computational analysis and symmetry constraints in terms of group-subgroup relations, we analysed the formation of the native crystalline structure of loellingite FeAs$_2$. We showed that the ground state of the material exhibits the ordered patterns of the electronic localization which are mainly associated with iron $3d_{x^2 - y^2}$ orbitals and can be characterized in terms of nematic-like ordering. The ordering is the result of the close interplay of the lattice and the electron degrees of freedom. In a structural aspect, it pursues an energy quest to select the orthorhombic crystal lattice attributed to the Pnnm space group. In a charge aspect, the ordering is connected with the valence charge density redistribution that not only provides a high electronic polarizability but also gives rise to an extra-large magnitude of the negative component of the dynamical p-d charge transfer.