Anharmonicity-induced strong temperature-dependent thermal conductivity in CuInX2 ( X=Se , Te)

Abstract

The lattice thermal $\mathrm{conductivity}({\ensuremath{\kappa}}_{\mathrm{L}}$) of most single crystals usually follows ${T}^{\ensuremath{-}1}$ temperature dependent relation at high temperature region. Here, we investigate the microscopic mechanism of the significant deviation of ${\ensuremath{\kappa}}_{\mathrm{L}}\ensuremath{\sim}{T}^{\ensuremath{-}1}$ rule in Cu-based chalcopyrite compounds $\mathrm{CuIn}{X}_{2}$($X$=Se, Te) by performing first-principles calculations and solving Peierls-Boltzmann transport equation with phonon anharmonic renormalization. The temperature sensitive second-order force constants lead to the dramatically softened optical phonon bands, which contributes to the enlarged phonon scattering phase space and consequent enhanced scattering rate. The strong temperature dependent thermal conductivity in $\mathrm{CuIn}{X}_{2}$($X$=Se, Te) can be well reproduced when calculating thermal conductivity with renormalization force constants. The motion of Cu contributes the most to the large anharmonicity at high temperature, which makes the anharmonic renormalization non-negligible for estimating accurate lattice dynamic and thermal conductivity. Our work will deepen the understanding of thermal transport property of Cu-based chalcopyrite, which is helpful for designing better thermoelectric or photovoltaic devices.