Researchers have discovered a predicted type of fermion that has mass in only one direction.

From the article:

Scientists have made a satisfying and intriguing physics discovery some 16 years after it was first predicted to be a possibility: a quasiparticle (a group of particles behaving as one) that only has an effective mass when moving in one direction.

In physics, mass generally refers to a property of particles that relates to things like their energy and resistance to movement. Yet not all mass is built the same – some describes the energy of a particle at rest, for example, while mass may also take into account the energy of a particle's motion.

In this case, the effective mass describes the quasiparticle's response to forces, which varies depending on whether the movement through the material is up and down, or back and forth.

Whereas regular quasiparticles have the same mass no matter what their direction of travel, the semi-Dirac fermion (to give it its technical name) being studied here doesn't seem to play by the normal rules.

Source: Science Alert

Author: David Nield