Spectroscopic signatures of domain walls in hexagonal ErMnO3

We measured the spectroscopic response of stripe- and vortex-containing ErMnO3 in order to uncover the electronic properties of the domain walls. We quantify Born effective charge and polarization differences using the lattice behavior, analyze the local rare earth environment from the f-manifold excitations, and reveal how shifts in the charge transfer excitations impact the band gap. The increased Born charge, polarization, and band gap in the vortex-containing material are brought together with a discussion of hybridization and wall density effects. The domain wall optical constants are strongly frequency dependent.