Surface-Tailored, Purely Electronic, Mott Metal-to-Insulator Transition

• Published in: Science (American Association for the Advancement of Science) Vol. 318; no. 5850; pp. 615 - 619
• Main Authors: Moore, R.G, Zhang, Jiandi, Nascimento, V.B, Jin, R, Guo, Jiandong, Wang, G.T, Fang, Z, Mandrus, D, Plummer, E.W
• Format: Journal Article
• Language: English
• Published: Washington, DC American Association for the Advancement of Science 26.10.2007; The American Association for the Advancement of Science
• Subjects: Buckling; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cooling; Crystal lattices; Crystallography; Distortion; Electrical phases; Electron states; Electronic structure; Electronic transport in condensed matter; Electronics; Energy gaps; Exact sciences and technology; Insulators; Lattices; Materials science; Metal-insulator transition; Metal-insulator transitions and other electronic transitions; Metals; Mineralogy; Mixed conductivity and conductivity transitions; Octahedrons; Phase transformations; Phonons; Physics; Strontium; Surface temperature; Temperature; Transition temperature; Compressive stress; Electrical conductivity; Lattice distortion; Metal-insulator transition; Order parameters; Property structure relationship; Mott transition; Symmetry breaking
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1145374

Mott transitions, which are metal-insulator transitions (MITs) driven by electron-electron interactions, are usually accompanied in bulk by structural phase transitions. In the layered perovskite Ca₁.₉Sr₀.₁RuO₄, such a first-order Mott MIT occurs in the bulk at a temperature of 154 kelvin on cooling. In contrast, at the surface, an unusual inherent Mott MIT is observed at 130 kelvin, also on cooling but without a simultaneous lattice distortion. The broken translational symmetry at the surface causes a compressional stress that results in a 150% increase in the buckling of the Ca/Sr-O surface plane as compared to the bulk. The Ca/Sr ions are pulled toward the bulk, which stabilizes a phase more amenable to a Mott insulator ground state than does the bulk structure and also energetically prohibits the structural transition that accompanies the bulk MIT.