FIG. 5: Intra- and inter-band contributions to χ$_{0}$ ( q , 0), top-panel for undoped and bottom-panel for 14% doped LaOFeAs. (a) and (d) are e − e , (b) and (e) are e − h and (c) and (f) are h − h contributions. 8 In order to investigate how the response of LaO$_{1}$ − $_{x}$F$_{x}$ FeAs is affected by the change in inter-band electronic transitions by separating the bands as follows: the first set consists of the two bands forming h -like FS sheets plus all the occupied bands and the second set consists of the all bands forming electron-like FS plus all the empty bands. Clearly such a grouping of the bands disregards band crossings ( e.g. , those of the e bands with filled states around M ). Fig. 5 shows static susceptibility resolved according to this criteria. Looking at various contributions around the Γ point it becomes clear that in both doped and undoped cases the low momentum susceptibility is dominated by the intra-band contribution ( e − e and h − h ). Doping leads to a strong reduction in the h − h contribution, which is expected since the effect of doping is to shrink the hole FS sheets around the Γ point. On the other hand around the M point and in the rest of the plane the inter-band e − h contributions dominate. Upon doping this inter-band contribution does not change substantially except in the very vicinity of the M point where a volcano like feature is formed. This can be easily understood as a consequence of the change of shape of the FS upon doping; the asymmetry between the e and h sheets becomes stronger resulting in a reduction of the strength of the nesting. 0.2 0.4 0.6 0.8 1 1.2 1.4 X M (a) 0.2 0.4 0.6 0.8 1 1.2 1.4 X M (d) 0.2 0.4 0.6 0.8 1 1.2 1.4 X M (e) 0.2 0.4 0.6 0.8 1 1.2 1.4 X M (b) 0.2 0.4 0.6 0.8 1 1.2 1.4 X M (c) 0.2 0.4 0.6 0.8 1 1.2 1.4 X M (f)