Large Thermal Hall effect observed in Bi₈₉Sb₁₂ topological insulator and Weyl Semimetal

Bi₈₉Sb₁₁ alloy, a topological insulator, becomes a Weyl semimetal in a magnetic field above a critical value H_C applied along the trigonal direction (001). We measured a Bi₈₉Sb₁₁ single crystal sample along the trigonal axis in a longitudinal magnetic field H>H_C. We observed large field-induced increases in the longitudinal electronic thermal conductivity along (001), which is mostly linear in field and maximal for 35K <T< 200K, attributed to the thermal chiral anomaly [1]. We report a large thermal Hall effect in the sample for the same temperature range: magnetic field applied along (001), heat flux along (010); transverse temperature gradient measured along (100), longitudinal gradient along (010). peaks at 0.07 in the temperature range 160K<T<200K. We will present the field dependence of the sample’s transport properties including thermopower, Nernst thermopower, Hall and electrical resistivity, and thermal conductivity, and discuss possible connections of this large thermal Hall effect to conveyor-belt entropy transport mediated by topologically protected Fermi arc surface states in Weyl semimetals [2].

References: [1] Dung Vu et al., arXiv:1906.02248 (2019), [2] McCormick et al., Phys. Rev. B 97, 195152 (2018).