First-principles insights into thermoelectric properties of topological nontrivial semimetal LiAuTe material

Abstract

Structural, electronic and thermoelectric properties of LiAuTe ternary compound are studied using density functional theory (DFT) and semi-classical Boltzmann transport theory. The cubic α -phase (space group F 4 ¯ 3m) is predicted to be ground state structure with a significant energy difference compared to honeycomb structure (space group P63mmc). The mechanical and dynamical stability of the α -phase is confirmed by calculating the elastic constants and phonon dispersion frequencies. At equilibrium lattice, with and without spin–orbit coupling, the LiAuTe compound band structure calculations show an s-p band inversion at Γ point, leading to a topological nontrivial semimetal phase. Thermoelectric parameters, such as Seebeck coefficient (S), electrical conductivity (σ), electronic (κ e ) and lattice (κ L ) thermal conductivities are computed. Electrons and holes relaxation times (τ) are also predicted. Hence, LiAuTe compound exhibits a low κ L value of 1.76 W mK−1 at room temperature which decreases with temperature increasing. At 900 K, κ L falls to 0.58 W mK−1 leading to a maximum ZT value of 0.52 at optimized n-doping concentration of 2.5 × 1020 cm−3. The present study reveals that LiAuTe compound is a suitable candidate for thermoelectric applications and will open new horizons for further researches on similar types of topological thermoelectric materials with better ZT.

Thermoelectric transport properties of surface states in three-dimensional topological insulator film

“…Thermoelectric transport, describing the process of thermoelectric conversion, is widely investigated in various systems, such as graphene [5,6], quantum dot [7,8], bismuth [9,10], superconductors [11,12], SiC nanoribbon [13,14], and so on. Recently, the discovery of topological insulators(TIs) provides new platform for the development of high-efficiency thermoelectric materials [15][16][17]. In particular, the three-dimensional(3D) TIs host topological surface states protected by the time-reversal symmetry [18][19][20][21][22][23].…”