Orbital-selective confinement effect of Ru $4d$ orbitals in SrRuO${}_3$ ultrathin film

Abstract

The electronic structure of SrRuO${}_3$ thin film with thickness from 50 to 1 unit cell (u.c.) is investigated via the resonant inelastic x-ray scattering (RIXS) technique at the O K-edge to unravel the intriguing interplay of orbital and charge degrees of freedom. We found that orbital-selective quantum confinement effect (QCE) induces the splitting of Ru $4d$ orbitals. At the same time, we observed a clear suppression of the electron-hole continuum across the metal-to-insulator transition (MIT) occurring at the 4 u.c. sample. From these two clear observations we conclude that QCE gives rise to a Mott insulating phase in ultrathin SrRuO${}_3$ films. Our interpretation of the RIXS spectra is supported by the configuration interaction calculations of RuO${}_6$ clusters.

arXiv comment7 pages, 7 figures

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• Detection of the Chiral Spin Structure in Ferromagnetic SrRuO${}_3$ Thin Film
• Capping and gate control of anomalous Hall effect and hump structure in ultra-thin SrRuO${}_3$ films
• Magnetic and electrical anisotropy with correlation and orbital effects in dimerized honeycomb ruthenate Li${}_2$RuO${}_3$