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

摘要: Dirac metals (gapless semiconductors) are believed to turn into Weyl when perturbations, which break either time reversal symmetry or inversion symmetry, employed. However, no experimental evidence has been reported for the existence of fermions in three dimensions. Applying magnetic fields near topological phase transition from a insulator band ${\mathrm{Bi}}_{1\ensuremath{-}x}{\mathrm{Sb}}_{x}$ we observe not only weak antilocalization phenomenon magnetoconductivity zero ($Bl0.4\text{ }\text{ }\mathrm{T}$), but also its upturn above 0.4 T $E//B$. This ``incompatible'' coexistence between and ``negative'' magnetoresistivity is attributed Adler-Bell-Jackiw anomaly (``topological'' $E\ifmmode\cdot\else\textperiodcentered\fi{}B$ term) presence corrections.