Dirac vs. Weyl in topological insulators: Adler-Bell-Jackiw anomaly in transport phenomena

Understand

Dirac metals (gapless semi-conductors) are believed to turn into Weyl metals when perturbations, which break either time reversal symmetry or inversion symmetry, are employed.

• However, no experimental evidence has been reported for the existence of Weyl fermions in three dimensions.
• Applying magnetic fields near the topological phase transition from a topological insulator to a band insulator in Bi1-xSbx, we observe not only the weak anti-localization phenomenon in magnetoconductivity near zero magnetic fields (B < 0.4 T) but also its upturn above 0.4 T only for E // B.
• This incompatible coexistence between weak anti-localization and negative magnetoresistivity is attributed to the Adler-Bell-Jackiw anomaly (topological E B term) in the presence of weak anti-localization corrections.