Multiple Weyl fermions in the noncentrosymmetric semimetal LaAlSi

Abstract

The noncentrosymmetric $R\mathrm{Al}\mathit{Pn}$ ($R=\mathrm{rare}\phantom{\rule{0.16em}{0ex}}\mathrm{earth}, Pn=\mathrm{Si}$, Ge) family, predicted to host nonmagnetic and magnetic Weyl states, provides an excellent platform for investigating the relation between magnetism and Weyl physics. By using high-field magnetotransport measurements and first principles calculations, we have unveiled herein both type-I and type-II Weyl states in the nonmagnetic LaAlSi. By a careful comparison between experimental results and theoretical calculations, nontrivial Berry phases associated with Shubnikov--de Haas oscillations are ascribed to the electron Fermi pockets related to both types of Weyl points located \ensuremath{\sim}0.1 eV above and exactly on the Fermi level, respectively. Under high magnetic field, signatures of Zeeman splitting are also observed. These results indicate that, in addition to the importance for exploring intriguing physics of multiple Weyl fermions, LaAlSi as a comparison with magnetic Weyl semimetals in the $R\mathrm{Al}\mathit{Pn}$ family would also yield valuable insights into the correlation between magnetism and Weyl physics.