phonon

phonon, in condensed-matter physics, a unit of vibrational energy that arises from oscillating atoms within a crystal. Any solid crystal, such as ordinary table salt (sodium chloride), consists of atoms bound into a specific repeating three-dimensional spatial pattern called a lattice. Because the atoms behave as if they are connected by tiny springs, their own thermal energy or outside forces make the lattice vibrate. This generates mechanical waves that carry heat and sound through the...