Fig. 2: Spectroscopic imaging characterization of the (2 × 2) charge modulation in Ba1−xKxFe2As2 (x ≈ 0.77). | Nature Communications

Fig. 2: Spectroscopic imaging characterization of the (2 × 2) charge modulation in Ba1−xKxFe2As2 (x ≈ 0.77).

From: Evidence for saddle point-driven charge density wave on the surface of heavily hole-doped iron arsenide superconductors

Fig. 2

a Topographic image of the As-terminated surface of Ba0.23K0.77Fe2As2 [(V, I) = (5 mV, 200 pA), image size: (13 nm)2]. b (Left panel) Normalised differential conductance L(x, V) = (dI/dV)/(I/V) as a function of bias and position spectra taken along the red line in a, (middle panel) its second-derivative with respect to position, and (right panel) the L(x) plots at bias voltages of  − 15 (red) and  + 15 mV (blue) extracted from the left panel, with each subtracted by the respective spatial average. c, d L(r, V) map slices obtained from a (10 nm)2 area on the As-terminated surface at energies of (c)  − 4 and (d)  + 4 mV respectively [(Vs, Is) = − 10 mV, 200 pA; \({V}_{{{{{\rm{mod}}}}}}=0.25\,{{{{\rm{mV}}}}}\)]. Dashed lines mark the same locations between the two map slices. e, f The associated Fourier transformations. Black circles highlight the Bragg peaks, red rectangles indicate the (2 × 2) charge order. g \(\tilde{g}({q}_{x},V)\) along Γ − M plot in bias voltage range between  − 80 and  + 80 mV showing the non-dispersive behaviour of the charge order peaks. h Zoomed-in of the L(r, V) map slice recorded at  − 10 mV, overlaid with a ball model of the Fe2As2 surface layer.

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