Observation of the Chiral-Anomaly-Induced Negative Magnetoresistance in 3D Weyl Semimetal TaAs

TLDR

Weyl semimetals, the 3D analog of graphene, host Weyl points near the Fermi level that give rise to chiral‑anomaly–related transport phenomena. The study aims to provide the first experimental evidence of chiral‑anomaly–induced negative magnetoresistance in the time‑reversal invariant Weyl semimetal TaAs. The experiment observed Shubnikov–de Haas oscillations at low fields and a π Berry phase, confirming Weyl points and demonstrating negative magnetoresistance due to the chiral anomaly.

Abstract

Weyl semi-metal is the three dimensional analog of graphene. According to the quantum field theory, the appearance of Weyl points near the Fermi level will cause novel transport phenomena related to chiral anomaly. In the present paper, we report the first experimental evidence for the long-anticipated negative magneto-resistance generated by the chiral anomaly in a newly predicted time-reversal invariant Weyl semi-metal material TaAs. Clear Shubnikov de Haas oscillations (SdH) have been detected starting from very weak magnetic field. Analysis of the SdH peaks gives the Berry phase accumulated along the cyclotron orbits to be {\pi}, indicating the existence of Weyl points.