Isotope Effect on Electron-Phonon Interaction in Multiband Superconductor MgB2

TL;DR

This study examines how isotope substitution affects electron-phonon interactions in MgB2, revealing a measurable shift in phonon coupling features that serve as benchmarks for understanding pairing mechanisms in superconductors.

Contribution

It provides the first direct measurement of isotope-induced shifts in electron-phonon coupling features in MgB2 using laser ARPES.

Findings

Isotope substitution shifts the phonon-related kink by ~3.5 meV.

The shift is unaffected by the superconducting transition.

Results establish benchmarks for isotope effects in superconductors.

Abstract

We investigate the effect of isotope substitution on the electron-phonon interaction in the multi-band superconductor MgB2 using tunable laser based Angle Resolved Photoemission Spectroscopy. The kink structure around 70 meV in the $\sigma$ band, which is caused by electron coupling to the E2g phonon mode, is shifted to higher binding energy by ~3.5 meV in Mg(10)B2 and the shift is not affected by superconducting transition. These results serve as the benchmark for investigations of isotope effects in known, unconventional superconductors and newly discovered superconductors where the origin of pairing is unknown.