Raman scattering study of spin-density-wave-induced anisotropic electronic properties in AFe2As2 (A=Ca,Eu)

TL;DR

This study uses polarization-resolved Raman scattering and theoretical calculations to investigate the anisotropic electronic properties induced by spin-density-wave order in AFe2As2 compounds, revealing orbital degeneracy lifting.

Contribution

It combines experimental Raman spectroscopy with DFT+DMFT calculations to elucidate the orbital origin of anisotropic electronic responses in SDW phases of AFe2As2.

Findings

Spectral weight redistribution in SDW phase

Anisotropic Raman response in CaFe2As2

Orbital degeneracy lifting of dxz/yz orbitals

Abstract

We present a polarization-resolved and temperature-dependent Raman scattering study of AFe2As2 (A = Ca, Eu). In the spin-density-wave (SDW) phase, spectral weight redistribution is observed in the fully symmetric and non-symmetric scattering channels at different energies. An anisotropic Raman response is observed in the fully symmetric channel in spontaneously detwinned CaFe2As2 samples. We calculate the orbital-resolved electronic structures using a combination of density functional theory and dynamical mean field theory (DFT+DMFT). We identify the electronic transitions corresponding to these two spectral features and find that the anisotropic Raman response originates from the lifted degeneracy of the dxz/yz orbitals in the broken symmetry phase.