Prediction of High Thermoelectric Performance of Pnictogen-dichalcogenide Layered Compounds with Quasi-one-dimensional Gapped-Dirac-like Band Dispersion

A theoretical guiding principle for designing high-performance thermoelectric materials has long been pursued. In this study [1], we theoretically demonstrate that pnictogen-dichalcogenide layered compounds, which originally attracted attention as a family of superconductors and have recently been investigated as thermoelectric materials [2], can exhibit very high thermoelectric performance. In particular, we clarify a promising guiding principle for materials design and find that LaOAsSe₂, a material that has yet to be synthesized, has a powerfactor that is six times as large as that of the known compound LaOBiS₂, and can exhibit a very large ZT under some plausible assumptions. This large enhancement of the thermoelectric performance originates from the quasi-one-dimensional gapped-Dirac-like band dispersion, which is realized by the square-lattice network of the p-orbitals. Our study offers one ideal limit of the band structure for thermoelectric materials. Because our target materials have high controllability of constituent elements and feasibility of carrier doping, experimental studies along this line are strongly awaited. [1] M. Ochi, H. Usui, and K. Kuroki, arXiv: 1706.09271 (2017). [2] Y. Mizuguchi et al., Cog. Phys. 3, 1156281 (2016).