Intrinsically Low Thermal Conductivity and High Carrier Mobility in Dual Topological Quantum Material, n‐Type BiTe

Abstract A challenge in thermoelectrics is to achieve intrinsically low thermal conductivity in crystalline solids while maintaining a high carrier mobility ( μ ). Topological quantum materials, such as the topological insulator (TI) or topological crystalline insulator (TCI) can exhibit high μ . Weak topological insulators (WTI) are of interest because of their layered hetero‐structural nature which has a low lattice thermal conductivity ( κ lat ). BiTe, a unique member of the (Bi 2 ) m (Bi 2 Te 3 ) n homologous series ( m : n =1:2), has both the quantum states, TCI and WTI, which is distinct from the conventional strong TI, Bi 2 Te 3 (where m : n =0:1). Herein, we report intrinsically low κ lat of 0.47–0.8 W m −1 K −1 in the 300–650 K range in BiTe resulting from low energy optical phonon branches which originate primarily from the localized vibrations of Bi bilayer. It has high μ ≈516 cm 2 V −1 s −1 and 707 cm 2 V −1 s −1 along parallel and perpendicular to the spark plasma sintering (SPS) directions, respectively, at room temperature.