Complex coincidence of superconducting and inverse proximity in quasi 2D nanostructured SnTe

Abstract

The induction of superconductivity in topological insulators and topological crystalline insulators is being investigated rigorously as a promising strategy for taking quantum spintronic applications to the next level. In this work, the complex interplay between topological and superconducting components is carefully tuned in such a way that an unusual coincidence of superconducting and inverse proximity is captured for the first time in the electrical transport properties of quasi two-dimensional nanostructured SnTe contacted using ‘s-wave’ superconducting electrodes. Ultralow temperature measurements in the complex superconducting proximity phase reveal two critical fields (H c2) of 0.9 T and 510 Oe. The lower H c2 is identified to be from the superconducting electrode while the higher one is attributed to the interface. The presence (absence) of coincidence between the upper critical field (H C2) extracted from Ginzburg–Landau theory and the Werthamer–Helfand–Hohenberg plot in the normal (inverse) superconducting proximity region and concurrent crossover in correlation lengths ξ(T) and L φ(T) are observed to be the manifestation of robust competition between the mutual domination of different mechanisms such as topological surface states and Cooper pair correlations. The current-dependent magnetoresistance measurements clearly demonstrate the dominant role of the interplay between the superconducting correlations and spin–orbit coupling. Interestingly, mere doubling of the contact area of the superconductor is observed to simultaneously enhance the critical field to ∼4 T and the transition temperature to ∼4.1 K in the interface region, suggesting the possibility of opening up a new gateway into nano-topological superconducting spintronic applications.