(pi,pi)-electronic order in iron arsenide superconductors

TL;DR

This paper reveals a (pi,pi) electronic order in iron arsenide superconductors that coexists with superconductivity and persists at high temperatures, challenging previous band structure calculations.

Contribution

It uncovers a (pi,pi) electronic order in Ba1-xKxFe2As2 that contradicts prior theoretical models and persists alongside superconductivity.

Findings

Discovery of (pi,pi) electronic order in Ba1-xKxFe2As2

Order coexists with superconductivity

Order persists up to room temperature

Abstract

The distribution of valence electrons in metals usually follows the symmetry of an ionic lattice. Modulations of this distribution often occur when those electrons are not stable with respect to a new electronic order, such as spin or charge density waves. Electron density waves have been observed in many families of superconductors[1-3], and are often considered to be essential for superconductivity to exist[4]. Recent measurements[5-9] seem to show that the properties of the iron pnictides[10, 11] are in good agreement with band structure calculations that do not include additional ordering, implying no relation between density waves and superconductivity in those materials[12-15]. Here we report that the electronic structure of Ba1-xKxFe2As2 is in sharp disagreement with those band structure calculations[12-15], instead revealing a reconstruction characterized by a (pi,pi) wave vector. This electronic order coexists with superconductivity and persists up to room temperature.