Researchers at PSI have investigated a novel crystalline material that exhibits electronic properties that have never been seen before.
It is a crystal of aluminum and platinum atoms arranged in a special way. In the symmetrically repeating unit cells of this crystal, individual atoms were offset from each other in such a way that they – as connected in the mind’s eye – followed the shape of a spiral staircase. This resulted in novel properties of electronic behaviour for the crystal as a whole, including so-called Rarita-Schwinger fermions in its interior and very long and quadruple topological Fermi arcs on its surface. The researchers have now published their results in the journal Nature Physics.
Researchers at the Paul Scherrer Institute PSI have found a new kind of quasiparticle. Quasiparticles are states in material that behave 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. Exactly these have now been detected experimentally for the first time – thanks in part to measurements at the Swiss Synchrotron Light Source SLS at PSI. “As far as we know, we are – simultaneously with three other research groups – among the first to see Rarita-Schwinger fermions”, says Niels Schröter, a researcher at PSI and first author of the new study.
Image: Niels Schröter (left) and Vladimir Strocov at their experimental station in the Swiss Light Source SLS at PSI.
Credit: Paul Scherrer Institute/Mahir Dzambegovic