Unveiling the Secrets of Crystal Vibrations

Researchers have made progress towards a complete theory of electrons and phonons in crystals, which is crucial for understanding their optical properties, conductivity, and superconductivity. By combining tools from quantum field theory and Feynman diagrams, the team derived a set of equations that describe the interaction between electrons and phonons. They addressed several challenges, including formulating the problem correctly, generalizing the theory to systems out of equilibrium, and providing the first complete set of diagrammatic Hedin-Baym equations. These advancements will aid in parameter-free simulations and downfolding methods, benefiting various fields such as photovoltaics and light-matter interactions.