The Peierls Distortion and Quasi-One-Dimensional Crystalline Materials of Indium Selenides

Recent investigations on thermoelectric research mainly focus on nano-structured low dimensional systems. It has been proven that the artificial structured nano-composites and superlattices have significant effect on lowering thermal conductivity. Peierls distortion is a pathway to enhance thermoelectric figure-of-merit ZT by employing natural nano-wire-like electronic and thermal transport. The phonon-softening, called Kohn anomaly, and Peierls lattice distortion decrease phonon energy and increase phonon scattering, respectively, result in lowering thermal conductivity. The quasi-one-dimensional electrical transport from anisotropic band structure ensures high Seebeck coefficient in Indium Selenide. In this chapter, we discuss the concept of Peierls transition and charge density wave in terms of mean field theory. As a toy model of charge density wave, we investigated the thermoelectric properties of CeTe ₂ and its doped compounds. The routes for high ZT materials development of In ₄Se _{3 − δ} are discussed from quasi-one-dimensional property and electronic band structure calculation to materials synthesis, crystal growth, and their thermoelectric properties investigations. The thermoelectric properties of In ₄Se _{3 − δ} need to be optimized indicating that further ZT can be achieved by electron doping. The chlorine doped In ₄Se _{3 − δ}Cl _0.03 compound exhibits high ZT over a wide temperature range and shows state-of-the-art thermoelectric performance of ZT= 1.53 at 450∘ C as an n-type materials.