Superconductivity in clathrate LiLaB8 with nontrivial band topology

Materials that exhibit both superconductivity and nontrivial topological electronic structures have attracted considerable attention due to the potential for the realization of novel quantum states. Here, using swarm-intelligence structure prediction methodology and first-principles calculations, we have predicted a ternary double-metal boron clathrate superconductor LiLaB8 with topologically protected surface states. B atoms in LiLaB8 polymerize into two kinds of caged structures, i.e. B-12 and B-24 cages, enclosing Li and La atoms, respectively. LiLaB8 can be possibly synthesized at the pressure above 75 GPa and recovered to ambient conditions with B cages well preserved. Electron-phonon coupling calculations show that LiLaB8 is a potential superconductor with an estimated T-c of 2.4 K at 100 GPa, which increases to 9.5 K at ambient pressure. The enhanced superconductivity is considered to originate from softened mode related to the vibrations of La and B atoms. Electronic band structure calculations showcase the apparent band inversion of La 5d and B 2p orbitals. Z(2) invariant and topologically protected surface states demonstrate that LiLaB8 is indeed a nontrivial-topological material. These results indicate LiLaB8 is a superconductor with nontrivial band topology that helps in the study of fascinating phenomena arising from the interplay of and superconductivity and band topology.

Automated summary

Using swarm-intelligence structure prediction methodology and first-principles calculations, a ternary double-metal boron clathrate superconductor LiLaB8 with topologically protected surface states has been predicted. It can possibly be synthesized under pressures above 75 GPa and recover to ambient conditions with well-preserved cages. The enhanced superconductivity originates from the vibrations of La and B atoms, while the band inversion of La 5d and B 2p orbitals indicates its nontrivial band topology. This study provides a platform for studying fascinating phenomena arising from the interplay of superconductivity and band topology.