Scientists have accidentally discovered a particle that has mass when it’s traveling in one direction, but no mass while traveling in a different direction. Known as semi-Dirac fermions, particles with this bizarre behavior were first predicted 16 years ago.

Summary

Scientists have discovered semi-Dirac fermions, particles that bizarrely gain or lose mass depending on the direction they travel.

Found in the semi-metal material ZrSiS, these quasiparticles are massless when moving at light speed in one direction but gain mass when slowing down in another, due to resistance within the material’s electronic structure.

This behavior, tied to Einstein’s E=mc², was unexpected and may lead to applications similar to graphene.

Researchers are now studying the unexplained quantum interactions behind this phenomenon, published in Physical Review X.

  • @[email protected]English
    62•2 days ago

    When the quasiparticles travel along one dimension inside the ZrSiS crystals, they do so at the speed of light and are therefore massless. But as soon as they try to travel in a different direction, they hit resistance, slow down and gain mass.

    Sounds more like a property of the material than the particle.

    Edit: did a little reading. It’s not even a real particle, it’s a quasi-particle, which apparently means it’s a general description of a group of particles.

    • @[email protected]English
      6•1 day ago

      Yup! PBS Spacetime has a nice video on quasi-particles, and how they are pretty much as “real” as protons and neutrons!

    • @[email protected]English
      3•22 hours ago

      I think a quasi-particle is more like a phenomenon that can mathematically be described in a way a particle would be, rather than just a group of particles. After all, holes in semiconductors are quasiparticles caused by a lack of real particles.

      Admittedly, I know very little about quasi-particles.