Paul Scherrer Institute's researchers have discovered a new kind of quasiparticle. Quasiparticles are states in the material that behaves in a certain way like actual elementary particles. The two physicists, William Rarita and Julian Schwinger, had predicted this type of quasiparticles in 1941, which came to be known as Rarita-Schwinger fermions. At present, these have been detected experimentally for the first time, courtesy of measurements at the Swiss Synchrotron Light Source, SLS at PSI. Niel Schroter, a researcher at PSI and first author of the new study, said that as far as they know, they are, simultaneously with three other research groups, among the first to see Rarita-Schwinger fermions.
While investigating a new material, exclusive aluminum platinum, the researchers discovered the quasiparticles. Schroter explained that when viewed with the naked eye, their crystal was simply a small cube, about half a centimeter in size and blackish-silverish. Their other colleagues at the Max Planck Institute for Chemical Physics of Solids in Dresden produced it using a unique process. In addition to the researchers in Dresden, scientists in Great Britain, Spain, and the US were also involved in the current study. The Dresden researchers aimed to achieve a tailor-made arrangement of the atoms in the crystal lattice.
It is precisely the combination of these two phenomena, the chirality and the topology of the crystal that leads to the unusual electronic properties that also differ inside the material and on its surface.
Though it was possible for the team to detect the Rarita-Schwinger fermions inside the material, complementary measurements at the English synchrotron radiation source Diamond Light Source revealed other exotic electronic states on the surface of the material: four so-called Fermi arcs, which are also significantly longer than any previously observed Fermi arcs.
Explaining further, Schroter said that it is quite clear that the Rarita-Schwinger fermions in the interior and these distinctive Fermi arcs on the surface are connected. Both result from the fact that it is a chiral topological material. The researchers were pleased that they were among the first to find such material. It is not just about these two electronic properties; the discovery of topological chiral materials will open up a whole playground of new exotic phenomena.
Researchers have a deep interest in new materials and the exotic behavior of electrons because some of them could be suitable for applications in the electronics of the future. The aim is, especially with quantum computers, to achieve ever denser and faster storage and data transmission in the future and to reduce the energy consumption of electronic components.
