Room Temperature Resonant Ultrasound Spectroscopy of Single Crystalline SnSe

Recently, the anisotropic single crystalline SnSe has gained tremendous interest as a promising thermoelectric material. The elastic constants of such anisotropic crystals are notoriously difficult to measure yet play a crucial role in many thermodynamic properties. We report for the first time the nine independent elastic constants of its stiffness tensor as measured by resonant ultrasound spectroscopy. Our experimental values of the elastic constants are in good agreement with those reported by the density functional theory of SnSe, except for C₁₂. The Voigt-Reuss-Hill method was used to determine the isotropic polycrystalline elastic moduli from the measured elastic constants of SnSe, which were found to be in agreement with theoretical values. Notably, the heat capacity of single crystalline SnSe deduced from our measured elastic moduli is in excellent agreement with the room temperature value of heat capacity determined from thermal transport measurements.