Figure 2
Zero-bias electronic and structural characterisation of the Fe chain. (a) STM topographic image of the Fe chain end (Vt=−11 mV, It=80 pA, scale bar=5 nm). The inset shows the section characterised in the rest of the figure. (b) STM topography at Vt=10 mV and I=10 pA. (c) Constant-height zero-bias AFM image of the chain end acquired at 5 K. In contrast to STM topography, the AFM image clearly resolves the atomic structure of the Fe chain. Each protrusion corresponds to single Fe atoms aligned in a straight manner along the Pb(110) rows (Fe inter-atomic distance=0.37 nm). In c, site 1 shows the MBS and 2 the presence of slightly misaligned atoms along the chain. (d) Zero-bias normalised conductance maps ∝ LDOS acquired at 5 K. At site 1 where the MBS is localised, a zero-bias conductance peak is clearly observed at 5 K and vanishes at 10 K as a result of the suppression of the superconductivity. The LDOS obtained at 10 K shown in the inset is homogeneous along the chain, whereas weak oscillations are observed at 5 K due to the MBS wavefunction decay. (e) Comparison of LDOS profiles extracted along the chain at 5 (black dots) and 10 K (grey dots). The orange curve shows a tentative fit of the LDOS with the theoretical MBS wavefunction to extract the two localisation lengths.
