Surface triggered stabilization of metastable charge-ordered phase in SrTiO3

Abstract

Abstract Charge ordering (CO), periodic modulation of electron density and lattice distortion, has been the fundamental subject in condensed matter physics, as well as a potential platform to induce novel functional properties. The charge-ordered phase is known to occur in a doped system of high d-electron occupancy but not of low occupancy. Here, we report that the charge-ordered phase is realized in electron-doped (100) SrTiO3 epitaxial thin films that have the lowest d-electron occupancy i.e., d1-d0. Theoretical calculation predicts the presence of a metastable CO state at the bulk state of electron-doped SrTiO3. Atomic scale analysis reveals that (100) surface distortion prefers the electron-lattice coupling for the charge-ordered state and triggers the stabilization for the CO phase from correlated metal, which extends up to six unit cells from the top surface to the interior. Our approach will provide an insight on the way to stabilize a new phase of matter that extends CO phase to the lowest electron occupancy, covering a whole range of 3d transition metal oxide.