An ab initio study of $\beta \text{−}{\mathrm{As}}_2{\mathrm{Te}}_3$ ($R\overline{3}m$ symmetry) at hydrostatic pressures shows that this compound is a trivial small band-gap semiconductor at room pressure that undergoes a quantum topological phase transition to a 3D topological Dirac semimetal around 2 GPa. At higher pressures, the band gap reopens and again decreases above 4 GPa. Our calculations predict an insulator-metal transition above 6 GPa due to the closing of the band gap, with strong topological features persisting between 2 and 10 GPa with ${\mathrm{Z}}_4=3$ topological index. By investigating the lattice thermal conductivity $\left({\kappa }_{\text{L}}\right)$, we observe that close to room conditions ${\kappa }_{\text{L}}$ is very low, either for the in-plane and the out-of-plane axis, with 0.098 and $0.023{\mathrm{Wm}}^{-1}{\mathrm{K}}^{-1}$, respectively. This effect occurs due to the presence of two low-frequency optical modes, namely ${\mathrm{E}}_u$ and ${\mathrm{E}}_g$, which increase the phonon-phonon scattering rate. Therefore, our results suggest that ultralow lattice thermal conductivities, which enable highly efficient thermoelectric materials, can be engineered in systems that are close to a structural instability derived from phonon Kohn anomalies. At higher pressures, the values of the in- and out-of-plane thermal conductivities not only increase in magnitude, but also approximate in value as the layered character of the compound decreases.

• Received 15 March 2021
• Accepted 29 June 2021

DOI:https://doi.org/10.1103/PhysRevB.104.024103