Ionic-bond-driven atom-bridged room-temperature Cooper pairing in cuprates and nickelates: a theoretical framework supported by 32 experimental evidences (2503.13104v2)

Abstract: Unlike ordinary conductors and semiconductors, which conduct electricity through individual electrons, superconductors usually conduct electricity through pairs of electrons, known as Cooper pairs. Even after 4 decades of intense study, no one knows what holds electrons together in complex high-$T_\mathrm{c}$ cuprates and nickelates. Here, targeting the critical challenge of the pairing mechanism behind high-$T_\mathrm{c}$ superconductivity in oxides, we create a new theoretical framework by standing on the foundation of the chemical-bond$\rightarrow$structure$\rightarrow$property relationship. Considering the dominance of eV-scale ionic bonding, affinity of O$^-$ (1.46 eV) and O$^{2-}$ (-8.08 eV) and large second ionization energy ($\sim$10-20 eV) of metal atoms, we propose a groundbreaking idea of electron e$^-$ (hole h$^+$) pairing bridged by oxygen O (metal M) atoms, i.e., the ionic-bond-driven e$^-$-O-e$^-$ (h$^+$-M-h$^+$) itinerant Cooper pairing, by following the principle of "tracing electron footprints to explore pairing mechanisms". Its correctness and universality are confirmed by 32 diverse experimental evidences, especially, the STM topographic image combining with small Cooper-pair size. Any other sub-eV and covalent-binding pairing mechanisms would be doubtful. Our findings resolve a 40-year puzzle of the microscopic mechanism for high-$T_\mathrm{c}$ superconductivity and validate the feasibility of room-temperature carrier-pairing in ionic-bonded superconductors, bringing the dream of room-temperature superconductivity one step closer.