Phonon anharmonicity in bulk ZrTe5

The study of phonon scattering processes is urgent for advancing the thermoelectric material with low thermal conductivity for commercial application. In this work, Raman scattering spectroscopy is utilized to quantify the temperature dependence of vibrational modes in ZrTe5 crystals, which enables the investigation on anharmonic contributions. We mainly focus on the temperature range from 80 up to 400 K due to noticeable surface oxidation at higher temperature. The phonon behaviors can be fully described by the model considering two mechanisms of the lattice thermal expansion effects and intrinsic anharmonicity. The four-phonon processes are non-negligible and even stronger than the three-phonon processes at high temperature. The phonon lifetime is greatly reduced by the enhancement of phonon scattering, contributing to the low thermal conductivity in ZrTe5 single crystals.