Multiple Weyl fermions in the noncentrosymmetric semimetal LaAlSi

TL;DR

This study uncovers both type-I and type-II Weyl fermions in nonmagnetic LaAlSi through magnetotransport measurements and calculations, highlighting its potential for exploring Weyl physics and magnetism relations.

Contribution

It provides the first experimental and theoretical evidence of multiple Weyl fermions in nonmagnetic LaAlSi, expanding understanding of Weyl semimetals beyond magnetic systems.

Findings

Identification of type-I and type-II Weyl states in LaAlSi.

Observation of nontrivial Berry phases linked to Weyl points.

Detection of Zeeman splitting under high magnetic fields.

Abstract

The noncentrosymmetric RAlPn (R = rare earth, Pn = Si, Ge) family, predicted to host nonmagnetic and magnetic Weyl states, provide 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 the Shubnikov-de Haas oscillations are ascribed to the electron Fermi pockets related to both types of Weyl points located ~ 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 RAlPn family would also yield valuable insights into the relation between magnetism and Weyl physics.