Strain-induced electronic phase transition and strong enhancement of thermopower of TiS2

Abstract

Using first principles density functional theory calculations, we show a semimetal to semiconducting electronic phase transition for bulk TiS 2 by applying uniform biaxial tensile strain. This electronic phase transition is triggered by charge transfer from Ti to S, which eventually reduces the overlap between Ti-(d) and S-(p) orbitals. The electronic transport calculations show a large anisotropy in electrical conductivity and thermopower, which is due to the difference in the effective masses along the in-plane and out of plane directions. Strain induced opening of band gap together with changes in dispersion of bands lead to three-fold enhancement in thermopower for both p- and n-type TiS2 . We further demonstrate that the uniform tensile strain, which enhances the thermoelectric performance, can be achieved by doping TiS2 with larger iso-electronic elements such as Zr or Hf at Ti sites.

arXiv comment8 pages, 6 figures

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• First-principles study on the electrical resistivity in zirconium dichalcogenides with multi-valley bands: mode-resolved analysis of electron-phonon scattering
• Ab-initio calculations of magnetic and optical properties of 3x3 supercell of TiX${}_2$ (X = S, Se and Te) compounds under the effect of externally applied electric field and strain