Strain Effect on Rashba Splitting and Phonon Scattering to Improve Thermoelectric Performance of 2D Heterobilayer MoTe${}_2$/PtS${}_2$

Abstract

Rashba spin-orbit coupling significantly modifies the electronic band structure in two-dimensional (2D) van der Waals (vdW) heterobilayers, which may enhance their thermoelectric (TE) properties. In this study, we use first-principles calculations and Boltzmann transport theory to explore the strain effect on the TE performance of the 2D vdW heterobilayer MoTe${}_2$/PtS${}_2$. A strong Rashba spin-splitting is observed in the valence band, resulting in an increase in the Seebeck coefficient for p-type. The lattice thermal conductivity of MoTe${}_2$/PtS${}_2$ is remarkably low about of 0.6 Wm${}^{-1}$K${}^{-1}$ at $T=300$ K due to large anharmonic scattering. Furthermore, biaxial strain enhances the power factor (PF) by introducing band convergence. At a strain of 2\%, the optimal PF for the n-type material reaches 170 $\mu$W/cmK${}^2$, indicating approximately 84.78\% increase compared to the unstrained state (92 $\mu$W/cmK${}^2$). Given the low lattice thermal conductivity, the optimized figure of merit $ZT$ achieves up to 0.88 at 900 K for n-type. Our findings indicate that MoTe${}_2$/PtS${}_2$ is a highly promising candidate for 2D heterobilayer TE materials, owing to its strong Rashba splitting and significant anharmonicity.

8 figures, 1 table