Non-monotonic temperature dependence of the thermal chiral anomaly in Bi(1-x)Sb(x) Weyl semimetals below 10K*

The chiral anomaly has been shown in the electrical and thermal conductivity in ideal Weyl semimetals induced by a magnetic field in Bi(1-x)Sb(x) alloy single crystals that are topological insulators in zero field. [1] The crystals have mobilities at 10 K in the 1,000,000 to 3,000,000 range, and carrier concentrations around 10^15 cm^-3, indicating that the chemical potential is at the Weyl points and that there are no trivial pockets to the Fermi surface. In those samples, the anomalous thermal conductivity, obtained with the field along the trigonal direction, has a maximum at 40 K due to a combination of a T^1 law due to the anomaly and a decrease in inter-Weyl-point scattering above about 50 K.  This theory predicts a monotonic decrease of the anomalous conductivity proportional to T at T<40 K. Here, we extend the thermal conductivity measurements of single crystal Bi(1-x)Sb(x) alloys to 2K. We report new experimental data that show a second maximum of thermal chiral anomaly at T= 4K. The anomalous thermal conductivity at 4K is about one order of magnitude larger than the theory predicts.