Observation of the chiral magnetic effect in ZrTe5

TL;DR

This paper reports the first experimental observation of the chiral magnetic effect in ZrTe_5, demonstrating a negative magnetoresistance consistent with theoretical predictions for Dirac and Weyl semimetals.

Contribution

It provides experimental evidence of the chiral magnetic effect in a condensed matter system, linking topological electronic structure with observable magnetotransport phenomena.

Findings

Observation of negative magnetoresistance with magnetic field parallel to current

Quadratic field dependence of magnetoconductance indicating chiral magnetic effect

Electronic structure consistent with a 3D Dirac semimetal

Abstract

The chiral magnetic effect is the generation of electric current induced by chirality imbalance in the presence of magnetic field. It is a macroscopic manifestation of the quantum anomaly in relativistic field theory of chiral fermions (massless spin $1/2$ particles with a definite projection of spin on momentum) -- a dramatic phenomenon arising from a collective motion of particles and antiparticles in the Dirac sea. The recent discovery of Dirac semimetals with chiral quasi-particles opens a fascinating possibility to study this phenomenon in condensed matter experiments. Here we report on the first observation of chiral magnetic effect through the measurement of magneto-transport in zirconium pentatelluride, ZrTe_5. Our angle-resolved photoemission spectroscopy experiments show that this material's electronic structure is consistent with a 3D Dirac semimetal. We observe a large negative magnetoresistance when magnetic field is parallel with the current. The measured quadratic field dependence of the magnetoconductance is a clear indication of the chiral magnetic effect. The observed phenomenon stems from the effective transmutation of Dirac semimetal into a Weyl semimetal induced by the parallel electric and magnetic fields that represent a topologically nontrivial gauge field background.