Absence of localized edge modes in spite of a non-trivial Zak phase in BiCu_{2}PO_{6}

Abstract

Topological properties of physical systems have attracted tremendous interest in condensed matter and atomic physics in the last decade. Recently, magnetic solid state compounds with and without magnetic order have become a focus. We provide evidence that BiCu_{2}PO_{6} is a gapful, disordered quantum antiferromagnet with a non-trivial finite Zak phase, which characterizes one-dimensional systems. Our calculations show that in spite of the non-trivial topology no localized edge modes occur. This unexpected behavior is explained by a generic feature, namely the significance of direct and indirect gaps in topological systems.