Origin of electronic phase separation in axion-insulator proximate Eu5In2Sb6

We propose a high-resolution x-ray diffraction study of the low-temperature phase-separation in Eu5In2Sb6. Our interest in this structural family is due to its perpendicular glide symmetries. On the one hand, this non-symmorphicity may give rise to topological crystalline insulating states like the elusive axion-insulator state. On the other hand, we discovered that it induces a phase separation between complex noncollinear magnetic regimes on a lengthscale of 90nm ~ 15um. One likely mechanism would be underlying structural inhomogeneities. Magnetoelastic coupling should allow us to distinguish the lattices of the two magnetic regimes. A multi-phase refinement could then reveal variations of the atomic positions and/or occupancies. Such detailed structural knowledge will be a prerequisite to reliably calculating the band topologies of this material. Proof of phase separation between topologically distinct (magnetically manipulable) insulating regimes would be an unprecedented result.