Fig. 5
From: Evidence of nematic order and nodal superconducting gap along [110] direction in RbFe2As2
Effect of atomic step edges on superconductivity. a Topography of a step edge along [100] direction (Vb = 0.5 V, I = 10 pA, scale bar: 20 nm). b Atomically resolved image near the [100] edge (Vb = 2 mV, I = 200 pA, scale bar: 2 nm), taken in the dashed rectangle in panel a. c Topography of a step edge along [110] direction (Vb = 0.5 V, I = 10 pA, scale bar: 20 nm). The orientation of the steps in panel a and c relative to the C4 symmetry breaking is indicated by the inserted vortex core images. d Line profiles along the dashed lines marked in panels a and c, showing that both steps are half a unit cell high. e, f Superconducting gap evolution when leaving the [100] step edge (along red arrow in panel a, setpoint: Vb = 1.5 mV, I = 80 pA, ΔV = 50 μV). A gap far from the step edge has been subtracted for panel f. Dashed lines mark the position of coherence peaks and EF. g, h Superconducting gap evolution when leaving the [110] step edge (along red arrow in panel of c, setpoint: Vb = 1.5 mV, I = 100 pA, ΔV = 50 μV) and the subtracted spectra. i ZBC decay evolution when leaving different steps (dots) and their exponential fits (solid lines). j, k Demonstration of the quasi-particle scattering on step edges with different orientation and pairing symmetry. j \(d_{x^2 - y^2}\)-wave pairing. k extended s-wave pairing with eight accidental nodes. (All the data shown in this figure are taken at T = 20 mK (Teff = 310 mK))
