Atomically Resolved Edge States on a Layered Ferroelectric Oxide

The emerging surface/edge electronic phases driven by broken symmetry effects have attracted great attention in low-dimensional electronic systems. However, experimental proof on their existence in ferroelectric oxides at the atomic scale is still missing. In this work, metallic surface states are observed on layered Bi2WO6 by scanning tunneling microscopy/spectroscopy. Differential conductance is remarkably enhanced near the step edge compared with that on the terrace, forming a one-dimensional edge state. Density functional theory calculations verify that symmetry breaking at the surface determines the electronic structures and O 2p orbitals contribute the most to the density of states around the Fermi level. Our discovery provides a new strategy toward the hidden phases on other correlated oxide surfaces.