A Topo-Superconducting Hybrid

Physics Soon after the discovery of topological insulators (TIs)—exotic materials that have a surface state similar to graphene's—physicists conjectured that “mating” a TI with a superconductor would give rise to an even more exotic state dubbed the topological superconductor (TSC); such a material might support Majorana states, thought to be a promising platform for quantum computing. A bulk TI can be doped until it becomes superconducting, while preserving its signature surface states. This approach led to the discovery of CuxBi2Se3, a possible TSC, but intrinsic inhomogeneities in that material made progress difficult. Now, Sasaki et al. observe a possible TSC state in Sn1-xInxTe by point-contact spectroscopy, which shows a signature peak in the density of states at the Fermi energy instead of the gap expected in an ordinary superconductor. Coupled with theoretical considerations, this result indicates that the material is an unconventional superconductor. The similarity in the band structure and the spin-orbit coupling strength in the two materials (CuxBi2Se3 and Sn1-xInxTe) suggests a more general approach in the search for topological superconductivity. Phys. Rev. Lett. 109 , 217004 (2012).