Experimental metrology to obtain thermal phonon transmission coefficients at solid interfaces

Interfaces between solids play a key role in heat conduction by phonons in applications ranging from heat dissipation in light-emitting diodes to waste heat recovery with thermoelectric devices. Despite their importance, our understanding of thermal phonon transport across interfaces lags far behind that of electrons and photons, with basic parameters such as transmission coefficients being largely unknown. In this work, the authors demonstrate an experimental approach that enables the measurement of phonon transmission coefficients at solid interfaces using experiments and a00exb i00exn00exi00ext00exi00exo computation. This work provides a unique microscopic window into the microscopic processes governing interfacial transport of terahertz-frequency thermal phonons that could impact numerous applications.