Leading role of satellite interstitial electrons in superconductivity in ternary superlithide Li14CP

The discovery of pressure-induced superconducting electrides has sparked a intense wave of interest in novel superconductors. However, opinions vary regarding the relationship between non-nuclear attractors (NNAs) and superconductivity, with two opposing views currently represented by the materials Li6P and Li6C. Here, we choose the ternary Li–C–P as a model system and reveal the underlying mechanism by which NNAs contribute to superconductivity. The loosely bound NNAs in the superlithide Li14CP covalently bond with Li and form unique satellite interstitial electrons (SIEs) around Li near the Fermi level, dominating the superconductivity. First-principles calculations show that the SIEs progressively increase in number and couple strongly with phonons at high pressure. Moreover, the Fermi surface nesting associated with SIEs induces phonon softening, further enhancing the electron–phonon coupling and giving the superlithide Li14CP a Tc of 10.6 K at 300 GPa. The leading role of SIEs in superconductivity is a general one and is also relevant to the recently predicted Li6P and Li6C. Our work presented here reshapes the understanding of NNA-dominated superconductivity and holds promise for guiding future discoveries and designs of novel high-temperature superconductors.