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

In a Dirac semimetal, each Dirac node is resolved into two Weyl nodes with opposite "handedness" or chirality. The two chiral populations do not mix. However, in parallel electric and magnetic fields ( E: || B: ), charge is predicted to flow between the Weyl nodes, leading to negative magnetoresistance. This "axial" current is the chiral (Adler-Bell-Jackiw) anomaly investigated in quantum field theory. We report the observation of a large, negative longitudinal magnetoresistance in the Dirac semimetal Na3Bi. The negative magnetoresistance is acutely sensitive to deviations of the direction of B: from E: and is incompatible with conventional transport. By rotating E: (as well as B: ), we show that it is…

• NS
  National Science Foundation

  Awards: DMR-1157490, DMR 1420541
• GA
  Gordon and Betty Moore Foundation

  Award: GBMF4539
• NH
  National High Magnetic Field Laboratory
• MU
  Multidisciplinary University Research Initiative

  Award: ARO W911NF-12-1-0461
• DO
  Division of Materials Research
• AR
  Army Research Office

  Award: ARO W911NF-11-1-0379