Spectroscopic Studies on the Metal–Insulator Transition Mechanism in Correlated Materials

• Published in: Advanced materials (Weinheim) 2018-10, Vol.30 (42), p.e1704777-n/a
• Main Authors: Kim, So Yeun, Lee, Min‐Cheol, Han, Garam, Kratochvilova, Marie, Yun, Seokhwan, Moon, Soon Jae, Sohn, Changhee, Park, Je‐Geun, Kim, Changyoung, Noh, Tae Won
• Format: Article
• Language: English
• Subjects: Electrical resistivity; electron–electron correlation; Insulators; MATERIALS SCIENCE; Metal-insulator transition; spectroscopy; Transition metal compounds; Transition metal oxides
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.201704777

The metal–insulator transition (MIT) in correlated materials is a novel phenomenon that accompanies a large change in resistivity, often many orders of magnitude. It is important in its own right but its switching behavior in resistivity can be useful for device applications. From the material physics point of view, the starting point of the research on the MIT should be to understand the microscopic mechanism. Here, an overview of recent efforts to unravel the microscopic mechanisms for various types of MITs in correlated materials is provided. Research has focused on transition metal oxides (TMOs), but transition metal chalcogenides have also been studied. Along the way, a new class of MIT materials is discovered, the so‐called relativistic Mott insulators in 5d TMOs. Distortions in the MO6 (M = transition metal) octahedron are found to have a large and peculiar effect on the band structure in an orbital dependent way, possibly paving a way to the orbital selective Mott transition. In the final section, the character of the materials suitable for applications is summarized, followed by a brief discussion of some of the efforts to control MITs in correlated materials, including a dynamical approach using light. The metal–insulator transition (MIT) is one of the most fascinating phenomena observed in correlated materials, with its switching behavior under various environmental perturbations leading to high potential for novel devices. The microscopic mechanisms of MITs in various correlated materials discovered through spectroscopic investigations are reviewed. Possible ways to control MITs in correlated materials are also discussed based on the findings.