Emergent fermions in solid state “universe”

The universe, with a continuum space-time and Lorentz invariance, has only three possible types of fermions in theory, namely, Dirac, Weyl and Majorana fermions. In reality, only Dirac-type elementary particles have been discovered. While it is still under debate whether any elementary particle of Weyl or Majorana types exists, all three types of fermions have been proposed to exist as emergent quasiparticles in solid state “universe”, which has discrete lattices without Lorentz invariance. Its 230 space groups in lattices (or 230 different solid state “universes”) can produce even more types of emergent fermions that are not allowed in the real universe. In this talk I will present on our experimental discoveries of Weyl fermion, “hourglass” fermion, and 3-compoment “new fermion” in solid state “universe”.