The determination of the electron–phonon interaction from tunneling data in the two-band superconductor MgB 2

Abstract

We calculate the tunneling density of states (DOS) of MgB 2 for different tunneling directions, by directly solving the real-axis, two-band Eliashberg equations (EE). Then we show that the numeric inversion of the standard single-band EE, if applied to the DOS of the two-band superconductor MgB 2, may lead to wrong estimates of the strength of certain phonon branches (e.g. the E 2 g ) in the extracted electron–phonon spectral function α 2 F( ω). The fine structures produced by the two-band interaction turn out to be clearly observable only for tunneling along the ab-planes in high-quality single crystals. The results are compared to recent experimental data.