Thermal chiral anomaly in the magnetic-field induced ideal Weyl phase of Bi1-xSbx topological insulators

Bi(1-x)Sb(x) alloys with x>9% are topological insulators. In a quantizing magnetic field applied along the trigonal direction, their bandgap decreases with field because the Zeeman energy exceeds the orbital Landau level energies. They turn into field-induced Weyl semimetals, with 6 pairs of 2 degenerate Weyl points centered around the L-points of the Brillouin zone. The Weyl point separation is mosty parallel to the applied field. It scales with magnetic field intensity. Because Bi and Sb are isoelectronic, the sample's unintentional doping levels can be kept minimum. Large single crystals with residual carrier concentrations in the 1E15 cm^-3 range and mobilities of the order of several million cm^2/V.s at 10K have been grown that have the chemical potential within a few meV of the Weyl point energy and reach the extreme quantum limit at 1-3 Tesla depending on x. This talk will review the thermal, thermoelectric and electrical properties of these ideal Weyl semimetals. The chiral anomaly is the dominant feature of the magnetoresistance, after care has been taken to avoid current jetting and geometrical magnetoresistane effects. The thermal chiarl anomaly (gravitational anomaly) increases the electronic thermal conductivity (x - 11%) by 300 % in a field of 9T, becoming also the dominant feature of the thermal conductivity The thermal effect are observed from 35 K (below which the lattice thermal conductivity dominates) to 200 K, almost twice the Debye temperature, which shows that the effect is robust to phonon scattering. It is observed in samples with mobilities as low as 50,000 cm^2/V.s at 10K, indicating robustness to defect scattering. The talk will further review the dependence of the effect to Sb concentration in the range 4%