Unidirectional mass quasiparticles found in ZrSiS crystal

For the first time, researchers have identified a quasiparticle that exhibits massless behavior in one direction, while possessing mass in the other. This elusive phenomenon, involving particles known as semi-Dirac fermions, was detected in a crystal of zirconium silicon sulfide (ZrSiS), a semi-metallic material. The discovery was detailed in the journal Physical Review

The research, led by Dr. Yinming Shao, assistant professor of physics at Penn State, involved using magneto-optical spectroscopy to study ZrSiS crystals. Speaking to Pennsylvania State University, Dr. Shao that they were not specifically looking for semi-Dirac fermions, but that the unexpected features in their data ultimately led to this first-ever observation. These quasiparticles, first theorized in 2008 and 2009, exhibit unique directional mass behavior depending on their motion, one concept theorist had dubbed the ‘B2/3 power law’.

Unique experimental techniques used

According to reports, the experiments were conducted at the National High Magnetic Field Laboratory in Florida, using one of the world’s strongest sustained magnetic fields: 900,000 times more powerful than Earth’s magnetic field. ZrSiS crystals were cooled to -452°F and exposed to infrared light under this magnetic field. According to According to reports, the observed energy patterns in the material revealed the distinctive behavior of semi-Dirac fermions, which matched theoretical predictions made more than a decade ago.

Future potential of ZrSiS

Dr. Shao noted in another statement that ZrSiS is a layered material similar to graphite that can be exfoliated into sheets for precise control, similar to graphene. He explained that understanding these quasiparticles could lead to important technological breakthroughs. Although their discovery solves one mystery, Dr. Shao also notes that many aspects remain unexplained, leaving plenty of room for further research.