Fig. 1: Planar heterojunctions between two dissimilar superconductors Pb and RhPb2.
From: Anomalous superconducting proximity effect of planar Pb–RhPb2 heterojunctions in the clean limit
a Schematic sketch of a planar Pb-RhPb2 heterojunction on graphitized SiC(0001) substrate, with the respective crystal structure shown in the top panel. b Three-dimensional STM topographic image (100 nm × 100 nm, V = 4.0 V, I = 5 pA) of a representative Pb–RhPb2 tricrystal heterojunction. As indicated, the Pb and RhPb2 superconductor films are well connected and form atomically sharp heterointerfaces. c Topographic profile measured along the black trajectory across various terraces in (b). d Zoom-in STM topography (40 nm × 40 nm, V = 12 mV, I = 1 nA) showing the atomically sharp heterointerface between Pb and RhPb2. Insert shows a FFT image of the p-RhPb2 surface, from which the in-plane lattice parameters of b = 6.8 Å and c = 5.9 Å are estimated by measuring the 2D reciprocal vectors b* and c*. e A series of dI/dV spectra (setpoint: V = 1.0 V, I = 500 pA) taken along the arrowed line from Pb to RhPb2 in (d). The topmost dI/dV spectrum is acquired on i-RhPb2 for comparison. f Low-energy-scale dI/dV spectra (setpoint: V = 4 mV, I = 500 pA) acquired at equal separations (4.6 nm), illustrating a spatial evolution of the superconducting gaps across a Pb/RhPb2 heterointerface. The bold curves are characteristic of i-RhPb2 (blue), the Pb/RhPb2 interface (black) and proximitized Pb (red), respectively. Vertical dashes mark the energy positions of the superconducting coherence peaks of intrinsic Pb (±ΔPb, see the red ones) and i-RhPb2 (±Δ, blue ones) at 0.4 K. The spectra in e and f have been offset vertically on the dI/dV intensity axis for clarity.
