Josephson current mediated by ballistic topological states in Bi 2 Te 2.3 Se 0.7 single nanocrystals

Superconducting proximity devices using low-dimensional semiconducting elements enable a ballistic regime in the proximity transport. The use of topological insulators in such devices is considered promising owing to the peculiar transport properties these materials offer, as well the hope of inducing topological superconductivity and Majorana phenomena via proximity effects. Here we demonstrate the fabrication and superconducting properties of proximity Josephson devices integrating nanocrystals single of Bi2Te2.3Se0.7 with a thickness of a few unit cells. Single junctions display typical characteristics of planar Josephson devices; junctions integrating two nanocrystals behave as nanodimensional superconducting quantum interference devices. A peculiar temperature and magnetic field evolution of the Josephson current along with the observed excess current effect point towards the ballistic proximity regime of topological channels. This suggests the proposed devices are promising for testing topological superconducting phenomena in two-dimensions. Topological insulators in contact with a superconductor could house unusual physical states such as Majorana fermions. Here, the authors fabricate and report the  electron-transport characteristics of Josephson junctions built using a nanoscale topological insulator, finding evidence for ballistic transport in the surface states of the nanocrystals.