Phonon structure in I-V characteristic of MgB$_{2}$ point-contacts

TL;DR

This paper investigates the phonon features in the I-V characteristics of MgB$_{2}$ point contacts, revealing how interband coupling and electron-phonon interactions influence the observed spectra.

Contribution

It applies a two-band model to analyze phonon structures in MgB$_{2}$ point-contact spectra, considering interband coupling effects on phonon features.

Findings

Phonon features are observed in $d^{2}V/dI^{2}(V)$ spectra.

Interband coupling affects phonon peculiarities due to the proximity effect.

Electron-phonon interactions are linked to the 2D-band in MgB$_{2}$.

Abstract

The search of the phonon structure at the above-gap energies was carried out for $d^{2}V/dI^{2}(V)$ spectra of MgB$_{2}$ point contacts with a normal metal. The two-band model is assumed not only for the gap structure in $dV/dI(V)$-characteristics, but also for phonons in $d^{2}V/dI^{2}(V)$ point-contact spectra, with up to the maximum lattice vibration energy. Since the current is carried mostly by charges of 3D-band, whereas the strong electron-phonon interaction occurs in 2D-band, we observe the phonon peculiarities due to ''proximity'' effect in {\it k}-space, which depends on the variation of interband coupling through the elastic scattering.