Surface triggered stabilization of metastable charge-ordered phase in SrTiO3

• Published in: Nature communications 2024-02, Vol.15 (1), p.1180-1180, Article 1180
• Main Authors: Eom, Kitae, Chung, Bongwook, Oh, Sehoon, Zhou, Hua, Seo, Jinsol, Oh, Sang Ho, Jang, Jinhyuk, Choi, Si-Young, Choi, Minsu, Seo, Ilwan, Lee, Yun Sang, Kim, Youngmin, Lee, Hyungwoo, Lee, Jung-Woo, Lee, Kyoungjun, Rzchowski, Mark, Eom, Chang-Beom, Lee, Jaichan
• Format: Article
• Language: English
• Subjects: 119/118; 132/122; 147/137; 639/301/119/544; 639/301/119/995; Condensed matter physics; Coupling; Electron density; electronic properties and materials; Electrons; Humanities and Social Sciences; multidisciplinary; Science; Science & Technology - Other Topics; Science (multidisciplinary); Stabilization; Strontium titanates; Surface distortion; surfaces, interfaces and thin films; Thin films; Transition metal oxides
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-45342-8

Charge ordering (CO), characterized by a periodic modulation of electron density and lattice distortion, has been a fundamental topic in condensed matter physics, serving as a potential platform for inducing novel functional properties. The charge-ordered phase is known to occur in a doped system with high d -electron occupancy, rather than low occupancy. Here, we report the realization of the charge-ordered phase in electron-doped (100) SrTiO 3 epitaxial thin films that have the lowest d -electron occupancy i.e., d 1 - d 0 . Theoretical calculation predicts the presence of a metastable CO state in the bulk state of electron-doped SrTiO 3 . Atomic scale analysis reveals that (100) surface distortion favors electron-lattice coupling for the charge-ordered state, and triggering the stabilization of the CO phase from a correlated metal state. This stabilization extends up to six unit cells from the top surface to the interior. Our approach offers an insight into the means of stabilizing a new phase of matter, extending CO phase to the lowest electron occupancy and encompassing a wide range of 3 d transition metal oxides. Charge order has been typically reported in doped systems with high d-electron occupancy. Here the authors demonstrate a charge-ordered insulating state in a La-doped SrTiO 3 epitaxial film which has the lowest d-electron occupancy and attribute it to surface distortion that favours electron-phonon coupling.