Scientists from Pennsylvania State University and Columbia University have teamed up to observe for the first time a special type of quasi particle - the semi Dirac fermion. These quasi particles have mass when moving in one direction, but lose mass when moving in another direction. Researchers say that conducting in-depth research on these quasi particles is expected to promote the development of next-generation technologies such as batteries and sensors. The relevant paper was published in the latest issue of Physical Review X. When the energy of a particle comes entirely from its motion, it has no mass. This means that it is essentially pure energy propagating at the speed of light, and photons moving at the speed of light are considered to have no mass. Albert Einstein's theory of special relativity also states that any object moving at the speed of light cannot have mass. However, the research team suggests that in solid materials, the "every move" of some particles that act in unison (also known as quasi particles) may be vastly different from that of individual particles. Some quasi particles only have mass when moving in one direction, while they have no mass when moving in another direction. They named these peculiar particles semi Dirac fermions. In 2008 and 2009, scientists from institutions such as the University of South Paris in France and the University of California, Davis, predicted the existence of semi Dirac fermions theoretically for the first time. In the latest research, assistant professor of physics at Pennsylvania State University, Yin Ming Shao, and others have for the first time glimpsed the true appearance of a semi Dirac fermion in a semi metallic material crystal called zirconium silicon sulfide (ZrSiS). The research team conducted experiments at the National High Magnetic Field Laboratory located in Florida. The continuous magnetic field generated by the mixed magnet in this laboratory can reach 900000 times that of the Earth's magnetic field, which can make small objects such as water droplets suspended. In the experiment, the research team cooled a piece of zirconium silicon sulfide to around -268.9 ℃ - only a few degrees higher than absolute zero - and then placed it in a strong magnetic field in the laboratory, irradiated it with infrared light, and then analyzed the light reflected by the material. With the help of a technique called magneto-optical spectroscopy, Shao Yinming and others observed the properties of quasi particles within zirconium silicon sulfide crystals. (New Society)