Anomalous electron-phonon interaction in doped LaOFeAs: a First Principles calculation

TL;DR

This paper uses first principles calculations to study electron-doped LaOFeAs, revealing how doping affects magnetic order and electron-phonon interactions, which may be crucial for understanding superconductivity near antiferromagnetic phases.

Contribution

It provides new insights into the magnetic and electron-phonon interactions in doped LaOFeAs, highlighting the role of vibrational coupling in superconductivity.

Findings

Doped LaOFeAs becomes non-magnetic at a critical electron concentration.

Enhanced electron-phonon interactions are induced by magnetism-vibration coupling.

Magnetism-vibration coupling may be key to superconductivity near antiferromagnetic phases.

Abstract

We present first principles calculations of the atomic and electronic structure of electron-doped LaOFeAs. We find that whereas the undoped compound has an antiferromagnetic arrangement of magnetic moments at the Fe atoms, the doped system becomes non magnetic at a critical electron concentration. We have studied the electron-phonon interaction in the doped paramagnetic phase. For the $A_{1g}$ phonon, the separation between the As and Fe planes induces a non-collinear arrangement of the Fe magnetic moments. This arrangement is anti parallel for interactions mediated by As, and perpendicular for Fe-Fe direct interactions, thus avoiding frustration. This coupling of magnetism with vibrations induces anharmonicities and an electron-phonon interaction much larger than in the pure paramagnetic case. We propose that such enhanced interactions play an essential role in superconducting compounds close to an atiferromagnetic phase transition.