bound state
system where a particle is subject to a potential such that the particle has a tendency to remain localised in one or more regions of space
exciton
quasiparticle which is a bound state of an electron and an electron hole
composite particle
quantum particle that is itself a system of other quantum particles bound by strong, weak or electromagnetic interaction
crystal
solid material whose constituent atoms, molecules, or ions are arranged in an ordered pattern extending in all three spatial dimensions
atomic nucleus
core of the atom; composed of bound nucleons (protons and neutrons)
Electron-hole droplets
condensed phase of excitons in semiconductors