Experimental evidence of giant chiral magnetic effect in type-II Weyl semimetal WP$_{2+\delta}$ crystals

TL;DR

This paper reports the first experimental observation of a giant chiral magnetic effect in type-II Weyl semimetal WP$_{2+ ext{delta}}$, characterized by negative resistivity and unique voltage-current behavior under specific conditions.

Contribution

It provides the first direct experimental evidence of a giant chiral magnetic effect in a Weyl semimetal, expanding understanding of chiral phenomena in condensed matter systems.

Findings

Observation of negative resistivity in WP$_{2+ ext{delta}}$

Voltage-current curves in second-fourth quadrant under specific conditions

Attribution of effect to higher coherent quantum state of Weyl fermions

Abstract

Chiral magnetic effect is a quantum phenomenon that is breaking of chiral symmetry of relativistic Weyl fermions by quantum fluctuation under paralleled electric field E and magnetic field B. Intuitively, Weyl fermions with different chirality, under stimulus of paralleled E and B, will have different chemical potential that gives rise to an extra current, whose role likes a chiral battery in solids. However, up to now, the experimental evidence for chiral magnetic effect is the negative longitudinal magnetoresistance rather than a chiral electric source. Here, totally different from previous reports, we observed the giant chiral magnetic effect evidenced by: 'negative' resistivity and corresponding voltage-current curves lying the second-fourth quadrant in type-II Weyl semimetal WP$_{2+\delta}$ under following conditions: the misaligned angle between E and B is smaller than 20$^\circ$, temperature <30 K and externally applied E<50 mA. Phenomenologically, based on macroscopic Chern-Simon-Maxwell equation, the giant chiral magnetic effect observed in WP$_{2+\delta}$ is attributed to two-order higher coherent time of chiral Weyl-fermion quantum state over Drude transport relaxation-time. This work demonstrates the giant chiral-magnetic/chiral-battery effect in Weyl semimetals.