Search for E_2g phonon modes in MgB_2 single crystals by point-contact spectroscopy

TL;DR

This study uses point-contact spectroscopy to detect E_2g phonon modes in MgB_2 single crystals, revealing their interaction with electrons and linking phonon features to superconducting properties, thus supporting harmonic phonon models.

Contribution

First direct observation of E_2g phonon modes in MgB_2 via point-contact spectroscopy and establishing their correlation with the superconducting gap.

Findings

Electron-phonon interaction with E_2g modes is resolved.

Correlation between E_2g mode intensity and superconducting gap is demonstrated.

Results support harmonic phonons model for MgB_2 superconductivity.

Abstract

The electron-phonon interaction in magnesium diboride MgB_2 single crystals is investigated by point-contact (PC) spectroscopy. For the first time the electron coupling with E_2g phonon modes is resolved in the PC spectra. The correlation between intensity of the extremely broad E_2g modes in the PC spectra and value of the superconducting gap is established. Our observations favor current theoretical models for electron-phonon mediated superconductivity in MgB_2 and they better match the harmonic phonons model.