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

Speaker: Prof. Ki-Seok Kim (Department of Physics, POSTECH, Korea)

Time: 3:30pm, Wednesday, Dec. 18, 2013 

Venue: Conference Hall 322, Science Building, Tsinghua University

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”  term) in the presence of weak anti-localization corrections.