Eliashberg function

Things become more difficult when one tries to measure the anisotropic Eliashberg function by means of the SC tunneling. The single-band numerical inversion program gives uncertain results, as was shown in Ref. [25]. 

Very rarely, (see [35]) the structure in d2V/dI2 which corresponds reasonably in shape to the phonon DoS (above 30 meV) was obtained. Thus, for this contact one can assume the observation of the inelastic PC spectrum for the 7r band, which is comparable to the Eliashberg EPI function for the same band calculated in Ref. [36]. Both experimental spectrum and 1r band Eliashberg function do not show the anomalously... 

Table 6.3 Eliashberg function and phonon contribution to decay for Einstein and Debye models.

Thus, considering results on y(H) only, a possible unconventional pairing in borocarbides cannot be ruled out. Similarly it has been noted by Dobrosavljevic-Grujic and Miranovic (2003) that a sizable anisotropy of the s-wave gap function leads to strong deviations for the specific heat in the superconducting state from the predictions of the one-band isotropic BCS-Eliashberg theory. In particular, at low temperatures gap-node like dependencies may appear. 

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