Connected Network Model for the Mechanical Loss of Amorphous Materials

We develop a theory of mechanical loss in amorphous solids based on the nonequilibrium thermodynamics of connected networks, providing a major advance beyond the quintessential two-level system (TLS) model, and revealing new avenues for the study amorphous materials. Atomistic modeling shows that TLS are not independent as typically assumed, but form a sparse, interconnected network. An analytical expression for mechanical loss is derived that systematically generalizes the existing TLS model and is shown to predict qualitatively distinct response. Amorphous mirror coatings with exceptionally low mechanical loss are critical components in the next generation of gravitational wave detectors.