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RESEARCHERS in Japan have uncovered the underlying structures and behaviour that give Si(111) its superconductive properties.
Si(111) is one of the thinnest two-dimensional materials ever created, consisting of individual indium metal atoms adsorbed on a silicon surface. The material was recently found to be superconductive. superconductors have effectively zero resistance and act as perpetual carriers of electric current with no need for a connected power source.
Normally, silicon surfaces comprise of individual terraces separated by steps, each the height of a single atom (‘atomic steps’). These steps could potentially interrupt, or decouple, neighboring terraces and break the current flowing over large surfaces.
Takashi Uchihashi and co-workers at the International Center for Materials Nanoarchitectonics, Tsukuba, together with scientists across Japan, used a scanning tunnelling microscope to verify how superconductivity occurs in the presence of atomic steps and terraces. The team applied different magnetic fields, which influenced the strength of the current and the presence of associated vortices.
By taking a series of images of the silicon, the team uncovered a pattern of supercurrent vortices present on the silicon surface. Two vortex types were present. Pearl vortices were present on the terrace surfaces, and appeared as bright round features in the images.
However, at the atomic steps the vortices appeared to become trapped, changing to become elongated “Josephson vortices”. These meant that the atomic steps work as so-called Josephson junctions, allowing coupling to occur across stepped terraces and enabling supercurrents to flow.
This discovery could eventually lead to materials engineered to have superconductivity properties.