Under various conditions of the growth process, when the presumably unconventional superconductor Sr2RuO4 (SRO) contains microinclusions of Ru metal, the superconducting critical temperature increases significantly. An atomic resolution high-angle annular-dark-field scanning transmission electron microscopy study shows a sharp interface geometry which allows crystals of SRO and of Ru metal to grow side by side by forming a commensurate superlattice structure at the interface. In an attempt to shed light on why this happens, we investigated the atomic structure and electronic properties of the interface between the oxide and the metal microinclusions using density functional theory calculations. Our results support the observed structure, indicating that it is energetically favored over other types of Ru-metal/SRO interfaces. We find that t2g-eg orbital mixing occurs at the interface with significantly enhanced magnetic moments. Based on our findings, we argue that an inclusion-mediated interlayer coupling reduces phase fluctuations of the superconducting order parameter, which could explain the observed enhancement of the superconducting critical temperature in SRO samples containing microinclusions.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics