Figure 4.
(a)–(f) The STM/S experimental results for zero-bias states trapped by interstitial Fe impurity in FeTe0.57Se0.43 [69]. (g)–(l) The STM/S experimental results for bound states trapped by the vortex in FeTe0.55Se0.45 [17,70]. (a) Topographic image of an isolated single interstitial Fe impurity (100 × 100 Å). (b) Zero-energy map for the area boxed in (a). (c) Spectra taken on top of and away from the interstitial Fe impurity. (d) Zero-energy peak value N(0) versus distance r from single interstitial Fe impurity. The solid curve is an exponential fit with ξ = 3.5 Å. Inset is a schematic image for the spatial distribution of interstitial Fe impurity scattering. (e) The spectra taken at the same interstitial Fe impurity at different temperatures. (f) The spectra taken at the same interstitial Fe impurity under different magnetic fields. The blue V-shaped dashed line is a guide to the eye showing the expected Zeeman splitting (g = 2). (g) A zero-bias conductance map (area 15 nm × 15 nm) around vortex cores. (h) A line-cut intensity plot along the black dashed line indicated in (g). (i) Evolution of zero-bias peaks with tunneling barrier measured at 0.55 K. GN = It/Vs, which corresponds to the energy-averaged conductance of normal states, and represents the conductance of the tunneling barrier. It and Vs are the STS setpoint parameters. (j) Temperature evolution of zero-bias peaks in a vortex core. The gray curves are numerically broadened 0.55 K data at each temperature. (k) Image of a single vortex in a 20 nm × 20 nm region measured at 0.48 K and 4 T. (l) Tunneling spectra measured along the arrowed lines marked 1 in (k) with increment steps of 7.6 Å. The dashed line shows the position of the zero-bias voltage. The discrete CdGM bound-state peaks can be clearly observed near the vortex core center.