Elastic wave transmission at an abrupt junction in a thin plate with application to heat transport and vibrations in mesoscopic systems

The transmission coefficient for vibrational waves crossing an abrupt junction between two thin elastic plates of different widths is calculated. These calculations are relevant to ballistic phonon thermal transport at low temperatures in mesoscopic systems and the Q for vibrations in mesoscopic oscillators, Complete results are derived in a simple scalar model of the elastic waves, and results for long-wavelength modes are obtained using full elasticity theory. We suggest that thin-plate elasticity theory provides a useful and tractable approximation to the three-dimensional geometry.