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

TL;DR

This paper reports experimental evidence of the Adler-Bell-Jackiw anomaly in topological insulators, demonstrating unique transport phenomena linked to Weyl fermions and topological phase transitions.

Contribution

It provides the first experimental observation of the Adler-Bell-Jackiw anomaly in three-dimensional topological insulators through magnetotransport measurements.

Findings

Observation of weak anti-localization near zero magnetic field

Detection of negative magnetoresistivity under parallel electric and magnetic fields

Attribution of phenomena to the Adler-Bell-Jackiw anomaly

Abstract

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.