Electron-phonon (lattice vibration) interaction showing drifting electron being scattered and heated (or cooled) by lattice vibration. This cools (heats) the lattice atoms. The interaction is presented by the quantum interaction Hamiltonian He-p, which includes the properties and the coupling of the phonon and electron. This interaction, in metals and semiconductors, is an important part of the heat transfer physics. In semiconductors this can be used to cool solids and harvest the phonon energy.