Electron-doped infinite-layer ${\mathrm{Sr}}_{1-x}{\mathrm{Eu}}_x\mathrm{Cu}{\mathrm{O}}_{2+y}$ films over a wide doping range have been prepared epitaxially on $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_3$(001) using reactive molecular beam epitaxy. In-plane transport measurements of the single-crystalline samples reveal a dome-shaped nodeless superconducting phase centered at $x\sim$ 0.15, a Fermi-liquid behavior and pronounced upturn in low-temperature resistivity. We show that the resistivity upturn follows square-root temperature dependence, suggesting the emergence of superconductivity via a three-dimensional percolation process. The percolative superconductivity is corroborated spectroscopically by imaging the electronic phase separation between superconducting and metallic phases with low-temperature scanning tunneling microscopy. Furthermore, we visualize interstitial and apical oxygen anions that rapidly increase in number as $x>$ 0.12 and elucidate their impacts on the superconductivity and normal-state resistivity.

Close

PrevNext

View figure in article

• Doping effects
• Local density of states
• Microphase separation
• Percolation
• Superconducting gap
• Cuprates
• High-temperature superconductors
• Mott insulators
• Ultrathin films
• Atomic force microscopy
• Molecular beam epitaxy
• Resistivity measurements
• Scanning tunneling spectroscopy
• X-ray diffraction