There is a type of quasiparticle, called a semi-Dirac fermion, that exists in a bizarre state where it has mass when moving in one direction but is massless when moving in a perpendicular direction. First predicted 16 years ago, physicists finally observed this behaviour in 2024 within a crystal of zirconium silicon sulfide (ZrSiS).

 There is a type of quasiparticle, called a semi-Dirac fermion, that exists in a bizarre state where it has mass when moving in one direction but is massless when moving in a perpendicular direction.

First predicted 16 years ago, physicists finally observed this behaviour in 2024 within a crystal of zirconium silicon sulfide (ZrSiS).