Orbital ordering and charge profile deformation in iron-based superconductors

Abstract

We investigate electronic structures of a typical iron-based superconductor LaFeAsO by first-principles calculations in order to clarify the ground-state of the mother compounds. With use of around mean field (AMF) for LDA+U formalism, we obtain an orbital ordered state showing relatively low magnetic moment widely for intermediate U values. In the low moment state, we find that electric quadrupole moment develops around iron atom, i.e., the charge profile deforms from a spherical to a collapsed one in contrast to the high moment state with almost zero quadrupole moment. Moreover, we examine As height dependence of the low moment state and find that the low moment state is also widely stable for a variation of As height compared to the high moment one.