Review on Electronic Correlations and the Metal-Insulator Transition in SrRuO₃

Abstract

The classical electron band theory is a powerful tool to describe the electronic structures of solids. However, the band theory and corresponding density functional theory become inappropriate if a system comprises localized electrons in a scenario wherein strong electron correlations cannot be neglected. SrRuO 3 is one such system, and the partially localized d-band electrons exhibit some interesting behaviors such as enhanced effective mass, spectral incoherency, and oppression of ferromagnetism and itinerancy. In particular, a Metal-Insulator transition occurs when the thickness of SrRuO 3 approaches approximately four unit cells. In the computational studies, irrespective of the inclusion of on-site Hubbard repulsion and Hund's coupling parameters, correctly depicting the correlation effects is difficult. Because the oxygen atoms and the symmetry of octahedra are known to play important roles in the system, scrutinizing both the electronic band structure and the lattice system of SrRuO 3 is required to find the origin of the correlated behaviors. Transmission electron microscopy is a promising solution to this problem because of its integrated functionalities, which include atomic-resolution imaging and electron energy loss spectroscopy.

Real‐Space Observation of Potential Reconstruction at Metallic/Insulating Oxide Interface

“…Indeed, transport and magnetic properties are known to behave differently for very thin SRO films (e.g., <4 u.c. [ 36 ] that can further couple to phononic modes [ 37 ] ) and similar behavior might exist for the SRO confined next to the interface. On the other hand, the strong increase of the electric field pointing toward the DSO (green color) is observed from the WP‐COMx and even more for the MA‐COMx map (Figure 3c).…”

Analysis of Metal-Insulator Crossover in Strained SrRuO3 Thin Films by X-ray Photoelectron Spectroscopy

“…Strontium ruthenate SrRuO 3 (SRO) is an itinerant ferromagnet and a prototypical spintronics system [8,9]. Because of the structural and chemical similarities of all oxide perovskites, the growth of very high-quality epitaxial SRO-based heterostructures is indeed possible, thus allowing to explore new perspectives in the field of electronic, magnetic and optical devices [10][11][12].…”