Oriented gap opening in the magnetically ordered state of Iron-pnicitides: an impact of intrinsic unit cell doubling on the $Fe$ square lattice by $As$ atoms

TL;DR

This paper demonstrates that considering intrinsic unit cell doubling due to arsenic atoms explains complex band reconstructions in magnetically ordered iron-pnictides, aligning with ARPES observations and emphasizing the importance of S4 symmetry.

Contribution

It introduces an S4 microscopic effective model that accounts for unit cell doubling, explaining band reconstruction and orbital order in magnetically ordered iron-pnictides.

Findings

Band reconstruction involves four points in unfolded Brillouin zone.

Small pockets or hot spots emerge without gaps at Fermi surfaces.

S4 symmetry favors staggered orbital order with C-AFM order.

Abstract

We show that the complicated band reconstruction near Fermi surfaces in the magnetically ordered state of iron-pnictides observed by angle-resolved photoemission spectroscopies (ARPES) can be understood in a meanfield level if the \emph{intrinsic unit cell doubling} due to As atoms is properly considered as shown in the recently constructed S$_{4}$ microscopic effective model. The (0,$\pi$) or ($\pi$,0) col-linear antiferromagnetic (C-AFM) order does not open gaps between two points at Fermi surfaces linked by the ordered wave vector but forces a band reconstruction involving four points in unfolded Brillouin zone (BZ) and gives rise to small pockets or hot spots. The S$_4$ symmetry naturally chooses a staggered orbital order over a ferro-orbital order to coexist with the C-AFM order. These results strongly suggest that the kinematics based on the S$_{4}$ symmetry captures the essential low energy physics of iron-based superconductors.