Pressure-induced superconductivity in the noncentrosymmetric Weyl semimetals LaAlX (X=Si,Ge)

In topological materials, Dirac fermions can split into two Weyl fermions with opposite chiralities due to the breaking of space-inversion symmetry, while in noncentrosymmetric superconductors, novel superconducting electron pairing mechanisms arise because of the antisymmetric spin-orbit coupling. In this work, we report the pressure-introduced superconductivity in a typical noncentrosymmetric Weyl semimetal $\mathrm{LaAl}X$ ($X=\mathrm{Si}$ and Ge). Superconductivity was observed at around 65 GPa without structural phase transition. A typical dome-shape phase diagram is obtained with the maximum ${T}_{\mathrm{c}}$ of 2.5 K (2.1 K) for LaAlSi (LaAlGe). Furthermore, the application of pressure does not destroy the nontrivial band topology of LaAlSi up to 80.4 GPa, making such materials potential candidates for realizing topological superconductivity. Our report of superconductivity in $\mathrm{LaAl}X$ ($X=\mathrm{Si}$ and Ge) will provide critical insight in noncentrosymmetric superconductors and stimulate further study on superconductivity in Weyl semimetals.