Direct observation of nodeless superconductivity and phonon modes in electron-doped copper oxide Sr${}_{1-x}$Nd${}_x$CuO${}_2$

Abstract

The microscopic understanding of high-temperature superconductivity in cuprates has been hindered by the apparent complexity of crystal structures in these materials. We used scanning tunneling microscopy and spectroscopy to study an electron-doped copper oxide compound Sr${}_{1-x}$Nd${}_x$CuO${}_2$ that has only bare cations separating the CuO${}_2$ planes and thus the simplest infinite-layer structure among all cuprate superconductors. Tunneling conductance spectra of the major CuO${}_2$ planes in the superconducting state revealed direct evidence for a nodeless pairing gap, regardless of variation of its magnitude with the local doping of trivalent neodymium. Furthermore, three distinct bosonic modes are observed as multiple peak-dip-hump features outside the superconducting gaps and their respective energies depend little on the spatially varying gaps. Along with the bosonic modes with energies identical to those of the external, bending and stretching phonons of copper oxides, our findings indicate their origin from lattice vibrations rather than spin excitations.

arXiv comment16 Pages, 4 figures, 5 supplemental figures

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Cited by in corpus (8)

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• Gigantic-oxidative atomic-layer-by-layer epitaxy for artificially designed complex oxides
• Percolative Superconductivity in Electron-Doped Sr${}_{1-x}$Eu${}_x$CuO${}_{2+y}$ Films
• Robust d-wave superconductivity from the Su-Schrieffer-Heeger-Hubbard model: possible route to high-temperature superconductivity
• Three-dimensional bond-order instability in infinite-layer nickelates due to nonlocal quantum interference
• Optical absorption in tilted geometries as an indirect measurement of longitudinal plasma waves in layered cuprates
• Exploring charge and spin fluctuations in infinite-layer cuprate SrCuO${}_2$ from a phonon perspective
• Angular dependence of the upper critical induction of clean $s$- and $d_{x^2-y^2}$-wave superconductors with self-consistent ellipsoidal effective mass and Zeeman anisotropies