O-bridged electron pairing: the microscopic mechanism for high-temperature superconductivity in cuprates and nickelates

Based on the energy level structure of neutral oxygen atom O and its anions, through in-depth analysis of the bonding process and formation mechanism of anion O${}^{x-}$ ($1<x\le 2$) in oxide superconductors dominated by ionic bonds, we propose an emerging and important novel idea of electron pairing with oxygen atoms as a bridge, different from the previously proposed electronic pairing schemes. This microscopic electronic pairing image is very intuitive and vivid, which can naturally explain the d-wave symmetry of Cooper pairs, large superconducting energy gaps, and small electron-pair sizes in copper oxide high-temperature superconductors. It is the electron-electron pairing mechanism mediated by oxygen atoms that directly determines the unconventional high-temperature superconductivity of cuprates and nickelates.