Quasiparticles

Scientists and engineers often describe elementary excitations in solids using the idea of quasiparticles. A quasiparticle is not a fundamental object such as an electron or an atomic nucleus. Instead, it is a collective excitation of many underlying particles that can be treated mathematically as if it were a single particle. Like real particles, quasiparticles carry energy and momentum, move through the lattice, scatter from impurities or one another, and follow well-defined dispersion relations. Casting the complex motion of countless atoms and electrons into a gas of interacting quasiparticles provides a powerful, intuitive framework for predicting and explaining the electronic, optical, and thermal behaviors of solids.