Symmetry breaking via orbital-dependent reconstruction of electronic structure in uniaxially strained NaFeAs

TL;DR

This study uses polarization-dependent ARPES with uniaxial strain to reveal orbital-dependent electronic structure reconstruction in NaFeAs's nematic phase, highlighting the role of spin polarization over ferro-orbital order.

Contribution

It demonstrates that orbital-dependent reconstruction in NaFeAs's nematic state is primarily driven by spin polarization, with minimal influence from ferro-orbital ordering.

Findings

Orbital-dependent reconstruction involves dxy and dyz bands.

Band splitting occurs due to hybridization of these orbitals.

dxz bands show energy shifts without reconstruction.

Abstract

The superconductivity discovered in iron-pnictides is intimately related to a nematic ground state, where the C4 rotational symmetry is broken via the structural and magnetic transitions. We here study the nematicity in NaFeAs with the polarization dependent angle-resolved photoemission spectroscopy. A uniaxial strain was applied on the sample to overcome the twinning effect in the low temperature C2-symmetric state, and obtain a much simpler electronic structure than that of a twinned sample. We found the electronic structure undergoes an orbital-dependent reconstruction in the nematic state, primarily involving the dxy- and dyz-dominated bands. These bands strongly hybridize with each other, inducing a band splitting, while the dxz-dominated bands only exhibit an energy shift without any reconstruction. These findings suggest that the development of orbital-dependent spin polarization is likely the dominant force to drive the nematicity, while the ferro-orbital ordering between dxz and dyz orbitals can only play a minor role here.