Electron-phonon coupling in BaFe<inf>2</inf>As<inf>2</inf>: A possible origin of nematic phase

Abstract

� 2015 Elsevier B.V. All rights reserved. Iron-based superconductors have the second-highest superconducting transition temperature next to cuprate superconductors. There are many electronic phases such as superconducting, antiferromagnetic and nematic phases, coexisting in the family of iron pnictides. The charge/spin orders are the key factors for understanding the mechanism of high-temperature superconductivity. In this paper we have performed a Raman scattering study of parent compound BaFe 2 As 2 . A relatively strong electron-phonon coupling is observed for B 1g phonon mode and is weakened after the structural transition at ∼140 K. Through a careful symmetry analysis, we revealed the possibility that B 1g mode can be effectively coupled with d xz and d yz orbits. The coupling can remove the degeneracy of the two orbits and further cause the fluctuations of electronic nematic phases. The study suggests that electron-phonon coupling can be a possible origin of nematic phase.