Fig. 2: Analysis of the SC gaps and bosonic mode energy in pristine CsV3Sb5.
From: Evidence of a distinct collective mode in Kagome superconductors
a Two types of representative dI/dV spectra. The bigger and smaller SC gaps corresponding to the peak-to-peak distances are labeled by \({\Delta }_{{{{\rm{b}}}}}\) and \({\Delta }_{s}\), respectively. b The corresponding derivative spectra d2I/dV2 of (a), where the energies of the SC gaps and the bosonic mode offset by the two gaps can be quantitatively extracted. Labels in (b) are defined as \({E}_{{s}{,}{b}}^{{{{{\rm{\pm }}}}}}{=}{\pm }({\Delta }_{{s}{,}{b}}{+}{\Omega })\), where Ω is the energy of bosonic mode. c Histograms of \({\Delta }_{{{{\rm{s}}}}}\), \({\Delta }_{{{{\rm{b}}}}}\), \({{|E}}_{s}|\), and \({{|E}}_{b}|\), plotted with the same counts of bins and fitted by normal distributions. The averaged values are \({\Delta }_{{{{\rm{s}}}}}\) = 0.40(0.09) meV, \({\Delta }_{{{{\rm{b}}}}}\) = 0.62(0.09) meV, \({{|E}}_{s}|\) = 1.16(0.09) meV, and \({{|E}}_{b}|\)=1.42(0.09) meV, where the error is based on the energy resolution. The extracted bosonic mode energy is 0.76(0.13) meV from \({{|E}}_{s}|\) and \({\Delta }_{{{{\rm{s}}}}}\), and 0.80(0.13) meV from \({{|E}}_{b}|\) and \({\Delta }_{{{{\rm{b}}}}}\). d A series of dI/dV spectra obtained on the Cs and Sb surfaces of CsV3Sb5 in different regions obtained under the tunneling conditions Vs = –2.0 mV, Vmod = 0.1 mV, It = 1 nA. The spatially-averaged spectrum is highlighted by the red solid line. e The derivative of the spatially-averaged dI/dV curve, from which the energies of the bosonic mode offset by the SC gaps (\({E}^{+}\) peak and \({E}^{-}\) dip in d2I/dV2) can be determined (\(\bar{\Omega }\) = 0.76 meV, \(\bar{\Delta }\) = 0.40 meV). f Two-gap Dynes functions description of the spatially-averaged dI/dV spectrum isolated from (d), showing good overall agreement. The difference between the two-gap Dynes functions and the experimental data demarcates the contribution due to the bosonic mode, which is marked by the shadowed region with cyan color. The two gap functions are shown as polar plots in the inset of (f).
