Design and Synthesis of Clathrate LaB8 with Superconductivity

Abstract

Boron-based clathrate materials, typically with three-dimensional networks of B atoms, have tunable properties through substitution of guest atoms, but the tuning of B cages themselves has not yet been developed. By combining crystal structural search with the laser-heated diamond anvil cell technique, we successfully synthesized a new B-based clathrate boride, LaB 8 , at ∼108 GPa and ∼2100 K. The novel structure has a B-richest cage, with 26 B atoms encapsulating a single La atom. LaB 8 demonstrates phonon-mediated superconductivity with an estimated transition temperature of 14 K at ambient pressure, mainly originating from electron-phonon coupling of B cage. The replacement of La with alkaline earth metals can remarkably elevate the transition temperature. This work creates a prototype platform for subsequent investigation on tunable electronic properties through the choice of captured atoms.