First-principles study of optical properties in incommensurate TlInSe₂ and TlInS₂

Abstract

The ternary thallium compound of TlInSe₂ shows the giant thermoelectric power in a low-temperature incommensurate phase below 410K, thus expected as a promising material for thermoelectric devices. TlInSe₂ exhibit a low dimensional nanostructure is Tl atoms arranged in one dimension, the optical anisotropy is measured. Similarly, TlInS₂ of Tl compounds exhibit a nanostructure that Tl is located in a two-dimensional, show the incommensurate phase at low temperatures. These material system, application to nano-devices and optical device materials also expected. In this work, we study electronic structures and optical properties of TlInSe₂ and TlInS₂ using the first-principles calculation and clarify the origins of their giant thermoelectric powers.