Record thermoelectric figure of merit in Bi1−xSbx achieved by 1-D Landau level quantization†

Abstract

Landau-level quantization confines electrons to a one-dimensional motion, generating a nearly δ-like energy distribution of the density of states that enhances the Seebeck coefficient and produces a high zT in an otherwise three-dimensional system. This mechanism is shown experimentally to create a record figure of merit of zT = 2.6 ± 0.26 at 100 K in an optimally n-type-doped single-crystalline Bi₈₈Sb₁₂ topological insulator, in a magnetic field of 0.4 T that is easily reached with permanent magnets. The result is confirmed to be reproducible on two samples and using two different measurement methods. The alloy is unique in that Landau levels are still distinct at 100 K. Quantization more than doubles the Seebeck coefficient and enhances the zT by a factor of 5 over the zero-field value, confirming the significant role that the quantum effect can play in thermoelectric research, especially in low-temperature cooling applications.