Signature of the chiral anomaly in a Dirac semimetal: a current plume steered by a magnetic field

Abstract

In this talk, we describe recent experimental progress in detecting the chiral anomaly in the Dirac semimetal Na${}_3$Bi in the presence of a magnetic field. The chiral anomaly, which plays a fundamental role in chiral gauge theories, was predicted to be observable in crystals by Nielsen and Ninomiya in 1983 [1]. Theoretical progress in identifying and investigating Dirac and Weyl semimetals has revived strong interest in this issue [2-6]. In the Dirac semimetal, the breaking of time-reversal symmetry by a magnetic field $\mathbf{B}$ splits each Dirac node into two chiral Weyl nodes. If an electric field $\mathbf{E}$ is applied parallel to $\mathbf{B}$, charge is predicted to flow between the Weyl nodes. We report the observation in the Dirac semimetal Na${}_3$Bi of a novel, negative and highly anisotropic magnetoresistance (MR). We show that the enhanced conductivity has the form of a narrowly defined plume that can be steered by the applied field. The novel MR is acutely sensitive to deviations of $\mathbf{B}$ from $\mathbf{E}$, a feature incompatible with conventional transport. The locking of the current plume to the field appears to be a defining signature of the chiral anomaly.

8 pages, 8 figures, based on a talk by NPO at APS March Meeting, San Antonio, 2015

References in corpus (1)

• Universal phase diagrams for the quantum spin Hall systems

Cited by in corpus (4)

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• Anisotropic and strong negative magneto-resistance in the three-dimensional topological insulator Bi2Se3
• Density wave instabilities and surface state evolution in interacting Weyl semimetals
• Anomalous magnetoconductivity and relaxation times in holography