Scientists from Pennsylvania State University and Columbia University in the United States have jointly observed a special type of quasiparticles-semi-Dirac fermions for the first time. Such quasiparticles possess mass when moving in one direction and lose mass when moving in another direction. Researchers said that in-depth study of these quasiparticles is expected to promote the development of next-generation batteries, sensors and other technologies. The relevant paper was published in the new issue of Physical Review X.
Research diagram. Image source: "Physical Review X"
When a particle derives its energy entirely from its motion, it has no mass. This means that it is essentially pure energy traveling at the speed of light, as a photon traveling at the speed of light is considered to have no mass. Albert Einstein's special theory of relativity also states that any object traveling at the speed of light cannot have mass.
However, the research team says that in solid materials, some particles that act in unison, also known as quasiparticles, can behave very differently from individual particles. Some quasiparticles only have mass when moving in one direction and no mass when moving in another direction. They named these strange particles semi-Dirac fermions.
In 2008 and 2009, scientists from the University of Paris-Sud in France and the University of California, Davis, in the United States, theoretically predicted the existence of semi-Dirac fermions for the first time.
In the latest research, Shao Yinming, assistant professor of physics at Pennsylvania State University, and others, for the first time glimpsed the "true content" of semi-Dirac fermions in a semi-metallic material crystal called zirconium silicon sulfide (ZrSiS).
The research team conducted experiments at the National High Magnetic Field Laboratory in Florida. The laboratory's hybrid magnet generates a continuous magnetic field that can reach 900,000 times the Earth's magnetic field, which can levitate small objects such as water droplets.
In the experiment, the research team cooled a piece of zirconium silicon sulfide to about -268.9°C - just a few degrees above absolute zero. They then placed it in the laboratory's powerful magnetic field and illuminated it with infrared light. They then analyzed the light reflected by the material. With the help of this technology called magneto-optical spectroscopy, Shao Yiming and others observed the properties of quasiparticles in zirconium silicon sulfide crystals.