Simultaneous Superconducting and Topological Properties in Mg–Li Electrides at High Pressures

Abstract

Electrides as a unique class of emerging materials exhibit fascinating properties and hold important significance for understanding matter under extreme conditions, which is characterized by valence electrons localized into the interstitial space as quasi-atoms (ISQs). In this work, using crystal structure prediction and first-principles calculations, we identified seven stable phases of Mg–Li that are electrides with novel electronic properties under high pressures. Among them, MgLi₁₀ is a semiconductor with a band gap of 0.22 eV, and Pm-3m MgLi is a superconductor with a superconducting transition temperature of 22.8 K. The important role played by the localization degree of ISQs in the superconducting transition temperature of these electrides is revealed by systematic comparison of Mg–Li with other Li-rich electride superconductors. Furthermore, we proved that Pm-3m MgLi and Pnma MgLi also have distinct topological behavior with metallic surface states and the nonzero Z₂ invariant. The simultaneous coexistence of superconductivity, electronic band topology, and electride property in the same structure of Pm-3m MgLi and Pnma MgLi demonstrates the feasibility of realizing multiquantum phases in a single material, which will stimulate further research in these interdisciplinary fields.