Oriented gap opening in the magnetically ordered state of iron pnictides: An impact of intrinsic unit cell doubling on the Fe square lattice by As atoms

¹ Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences P. O. Box 603, Beijing 100190, China
² Department of Physics, Purdue University - West Lafayette, IN 47907, USA

Received: 7 December 2013
Accepted: 9 December 2013

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 mean-field level if the intrinsic unit cell doubling due to As atoms is properly considered as shown in the recently constructed S₄ microscopic effective model. The or collinear 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 the unfolded Brillouin zone (BZ) and gives rise to small pockets or hot spots. The S₄ 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 S₄ symmetry captures the essential low-energy physics of iron-based superconductors.