Coherent acoustic phonon dynamics facilitating acoustic deformation potential characterization of Mg3Sb2

Acoustic deformation potential (ADP) quantifies carrier-acoustic phonon coupling and is essential for dissecting transport physics in thermoelectrics. Herein, we report the use of ultrafast spectroscopy of coherent acoustic phonons (CAPs) to characterize the ADP of thermoelectric materials, using Mg3Sb2 as an example. The photon energy-dependent amplitudes of the CAP-induced oscillatory reflectance were used to determine the ADP coupling constant, agreeing well with that from first-principles calculations. This method relies on the transient Coulombic interaction between carriers and acoustic phonons, free of influence from other scattering channels. It is shown that the method is particularly feasible for the study of thermoelectric materials, because their common features of strong phonon anharmonicity and small band gaps make the measurement insensitive to the uncertainty of carrier diffusion coefficients, ensuring its accuracy.

Automated summary

In this study, ultrafast spectroscopy of coherent acoustic phonons was used to characterize the ADP of thermoelectric materials, specifically Mg3Sb2. The method relies on the transient Coulombic interaction between carriers and acoustic phonons, and is free from other scattering channels. It is particularly feasible for studying thermoelectric materials due to their strong phonon anharmonicity and small band gaps, ensuring measurement accuracy.