Edge States and Enhanced Superconducting Gaps in Bi Islands on FeTe0.55Se0.45

Abstract By measuring scanning tunneling spectroscopy on some large Bi islands deposited on FeTe 0.55 Se 0.45 superconductors, we observe clear in-gap edge states with double peaks at about ±1.0 meV on the spectra measured near the perimeter of the islands. This feature is very different from the single zero-energy peak observed on some other small Bi islands. The edge states spread towards the inner side of the islands over a width of 2–3 nm. The two edge-state peaks at positive and negative energies move to higher values with the increase of the magnetic field, and they disappear near the transition temperature of FeTe 0.55 Se 0.45 . Meanwhile, enhanced superconducting gaps are observed in the central regions of these Bi islands, which may be induced by the enhanced pair potential of the topological surface state. Our observations provide a valuable message for the edge state and the proximity-induced superconductivity on specific Bi islands grown on FeTe 0.55 Se 0.45 substrate.