Ultralow lattice thermal conductivity in topological insulator TlBiSe2

We present ab-initio calculations of the phonon thermal transport properties of topological insulator TlBiSe2. Our results point to a very low lattice thermal conductivity, comparable or lower than those of some popular good thermoelectric materials. Furthermore, we find a slight thermal anisotropy between the in-plane and cross-plane directions in TlBiSe2, markedly smaller than those of van-der-Waals topological insulators explored so far. These conclusions are confirmed and explained by comprehensive analysis of the phonon spectrum of TlBiSe2. The combination of ultra-low lattice thermal conductivity and small anisotropy makes TlBiSe2 a promising candidate for thermoelectric applications. Published by AIP Publishing.