Electronic Topological Transition as a Route to Improve Thermoelectric Performance in Bi_0.5Sb_1.5Te₃

The electronic structure near the Fermi surface determines the electrical properties of the materials, which can be effectively tuned by external pressure. Bi_0.5Sb_1.5Te₃ is a p-type thermoelectric material which holds the record high figure of merit at room temperature. Here we examine whether the figure of merit of this model system can be further enhanced through some external parameter. With the application of pressure, we surprisingly find the power factor of this material exhibits λ behavior with a high value of 4.8 mW m⁻¹K⁻² at pressure of 1.8 GPa. Such an enhancement is found to be driven by pressure-induced electronic topological transition, which is revealed by multiple techniques. Together with a low thermal conductivity of about 0.89 W m⁻¹K⁻¹ at the same pressure, a figure of merit of 1.6 is achieved at room temperature, which is the record high value for any known p-type thermoelectric materials discovered so far. The results and findings highlight the electronic topological transition as a new route for improving the thermoelectric properties.