Classifying Induced Superconductivity in Atomically Thin Dirac-Cone Materials

Recently, Kayyalha et al. ( Phys. Rev. Lett., 2019, 122, 047003) reported on the anomalous enhancement of the self-field critical currents ( I c(sf, T)) at low temperatures in Nb/BiSbTeSe 2-nanoribbon/Nb Josephson junctions. The enhancement was attributed to the low-energy Andreev-bound states arising from the winding of the electronic wave function around the circumference of the topological insulator BiSbTeSe 2 nanoribbon. It should be noted that identical enhancement in I c(sf, T) and in the upper critical field ( B c2( T)) in approximately the same reduced temperatures, were reported by several research groups in atomically thin junctions based on a variety of Dirac-cone materials (DCM) earlier. The analysis shows that in all these S/DCM/S systems, the enhancement is due to a new superconducting band opening. Taking into account that several intrinsic superconductors also exhibit the effect of new superconducting band(s) opening when sample thickness becomes thinner than the out-of-plane coherence length (ξ c(0)), we reaffirm our previous proposal that there is a new phenomenon of additional superconducting band(s) opening in atomically thin films. View Full-Tex