Mode Wise Thermal Conductivity of Bismuth Telluride

Abstract

Thermal properties and transport control are important for many applications, for example, low thermal conductivity is desirable for thermoelectrics. Knowledge of modewise phonon properties is crucial to identify dominant phonon modes for thermal transport and to design effective phonon barriers for thermal transport control. In this paper, we adopt timedomain (TD) and frequencydomain (FD) normalmode analyses to investigate modewise phonon properties and to calculate phonon dispersion relations and phonon relaxation times in bismuth telluride. Our simulation results agree with the previously reported data obtained from ultrafast timeresolved measurements. By combining frequencydependent anharmonic phonon group velocities and lifetimes, modewise thermal conductivities are predicted to reveal the contributions of heat carriers with different wavelengths and polarizations.