Research teams such as Tohoku University, Osaka University, Kyoto Sangyo University, and the University of Cologne, Germany have developed a method for converting ordinary superconductors into topological superconductors.
Topological insulators discovered about 10 years ago have an insulator inside, whereas their edges (surface in 3D, edges in 2D) move in a solid with zero mass. A conduction path caused by the "dirak electron" appears.With this discovery as an opportunity, "topological superconductors", which are the development materials of topological insulators, have been attracting attention, but there is still no definitive evidence.
In order to realize topological superconductivity, the "superconducting proximity effect" is generally used.For example, when a topological insulator and a superconductor are joined, an electron pair (Cooper pair) responsible for superconductivity invades from the superconductor side to the topological insulator side, so that it exists near the interface between the two substances. Dirac electrons are superconducted.However, with this method, the special particles "Majorana particles" that are predicted to appear at the edges of topological superconductors are buried near the interface inside the material, making it difficult to detect them. There was the problem that no definitive evidence could be obtained.
Under these circumstances, the researchers created an ultra-thin film of Pb (lead), which is an ordinary superconductor, on the surface of the topological insulator TlBiSe2, and investigated its electronic state. As a result, it was originally on the surface of the topological insulator. It was discovered that the dilac electrons moved to the Pb surface by bonding.Furthermore, when the energy state of the Pb thin film is measured, a "superconducting gap" indicating that the Dirac electrons have become superconducting is observed, and Pb, which is an ordinary superconductor, has changed to a topological superconductor. Was found.
This result suggests that topological superconductivity can be realized without using the superconducting proximity effect, and it is expected that Majorana particles will be detected in this system in the future.
Paper information:[Nature Communications] Conversion of a conventional superconductor into a topological superconductor by topological proximity effect
