Superconductivity and superionic behaviors of Kagome lattices in Li–Si compounds under high pressure

Abstract

The formation of Kagome lattices by interstitial quasi-atoms (ISQs) in P6/mmm phases provides a platform for exploring interactions between topology and correlation physics. In this study, Li₅X (X = Si, Ge, Sn, and Sb) compounds are investigated at pressures of 0, 50, and 100 GPa, and Dirac bands, flat bands, and Van Hove singularities in the energy bands for their stabilized P6/mmm phases are presented. Meantime, the structures of Li_xSi (x = 1–8) compounds at pressures of 0, 50, 100, and 150 GPa are predicted, and their structural features are discussed in terms of high-coordination and two-dimensional layering. The localized space of ISQs in the Kagome lattice is discussed, which is characterized by a triangular bipyramid and a quadrangular bipyramid. The formation of the Kagome lattice from Li atoms is observed in the predicted Li₃Si-P6/mmm. In addition, the superconducting transition temperature of Li₅Si-P6/mmm is calculated to be 2.9 K at 50 GPa. At a pressure of 50 GPa and temperatures of 1800 and 1100 K, Li atoms in Li₅Si-P6/mmm and Li₆Si-C2/m undergo melting and enter the superionic state, indicating superionic electride behavior. Finally, temperature-pressure phase diagrams of Li₅Si-P6/mmm, including superconducting, solid, superionic, and liquid states at pressures of 50 and 100 GPa are reported.