Physicists Find Particle That Only Has Mass When Moving in One Direction : ScienceAlert

Some 16 years after first predicting this possibility, scientists have made a satisfying and interesting physical discovery: quasiparticle (a group of particles that behave like one) has effective mass only when moving in one direction.

In physics, mass usually refers to an attribute of a particle, related to its energy and resistance to motion. However, not all masses are the same – for example, some describe the energy of a particle at rest, while mass may also take into account the energy of a particle in motion.

In this case, the effective quality describes quasiparticleThe response to force depends on whether the material is moving up and down or back and forth.

And regular quasiparticle Semi-Dirac particles have the same mass regardless of the direction of travel Fermions (Give it a technical name) Research seems to go against normal rules here.

This discovery could lead to fundamental changes in: quantum physics and electronic sensors.

The new quasiparticle was discovered by an international team of scientists inside a ZrSiS semimetal crystal that was cooled to -452 degrees Fahrenheit (or -269 degrees Celsius) – an extreme condition for an extremely rare quasiparticle .

Particles can generally be described as boson or Fermionsdepends on the measurement of a property called spin. Dirac fermions—either in their canonical or quasi-particle form—have the opposite properties of their particle and antiparticle forms.

The semi-Dirac fermions detailed in the new study are strange beasts that have so far only existed theoretically, with very different energy guidelines in the vertical direction.

“It was completely unexpected,” explain Condensed matter physicist Shao Yinming from Penn State University. “When we started studying this material, we weren’t even looking for semi-Dirac fermions, but we saw signatures we didn’t understand.”

“It turns out that for the first time we have observed these wild quasiparticles that sometimes move as if they have mass and sometimes move as if they have no mass.”

The researchers used a method called the “scientific analytical method” Magneto-optical spectroscopy when they made this discovery. Here, materials are studied through the reflection of infrared light they emit under the influence of strong magnetic fields.

And we do mean strong: about 900,000 times stronger than the Earth’s magnetic field, courtesy of the National High Magnetic Field Laboratory in Florida. These are the exotic conditions scientists use to study the rarest interactions at the smallest scales.

From there, with the help of some numerical models, semi-Dirac fermion activity was observed and identified: no quality in one direction (all its energy is described by its motion), but has effective mass in the other direction. Fortunately for non-physicists, researchers provide an analogy.

“Imagine that the particle is a tiny train confined in a network of tracks, which is the underlying electronic structure of the material,” explain Shao.

“Now, at certain points the tracks intersect, so our particle train is moving along its fast track at the speed of light, but then it hits an intersection and needs to switch to a vertical track.

“Suddenly, it experiences resistance, and it has mass. The particles are either all energy or they have mass, depending on the direction in which they ‘track’ along the material.”

This is a noteworthy moment for the world of physics, including those First assume phenomenon in 2008.

“The most exciting part of this experiment is that the data cannot be fully explained,” explain Shao.

“There are a lot of unanswered questions about what we’re observing, so that’s what we’re trying to understand.”

The study was published in Physical ReviewX.