Evidence for the chiral anomaly in the Dirac semimetal Na 3 Bi

Abstract

Breaking chiral symmetry in a solid Dirac semimetals have graphene-like electronic structure, albeit in three rather than two dimensions. In a magnetic field, their Dirac cones split into two halves, one supporting left-handed and the other right-handed fermions. If an electric field is applied parallel to the magnetic field, this “chiral” symmetry may break: a phenomenon called the chiral anomaly. Xiong et al. observed this anomaly in the Dirac semimetal Na 3 Bi (see the Perspective by Burkov). Transport measurements lead to the detection of the predicted large negative magnetoresistance, which appeared only when the two fields were nearly parallel to each other. Science , this issue p. 413 , see also p. 378