In physics, a Dirac fermion is a spin-½ particle (a fermion) which is different from its antiparticle.
A vast majority of fermions fall under this category.
In particle physics, all fermions in the standard model have distinct antiparticles (perhaps excepting neutrinos) and hence are Dirac fermions.
In condensed matter physics, low-energy excitations in graphene and topological insulators, among others, are fermionic quasiparticles described by a pseudo-relativistic Dirac equation.
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