Anharmonicity and self-energy effects of the E2g phonon in MgB2

TL;DR

This study investigates the anharmonicity and self-energy effects of the E2g phonon in MgB2 using Raman scattering, revealing anharmonic decay as the main cause of linewidth and superconductivity-related phonon frequency shifts.

Contribution

It provides new insights into the phonon anharmonicity and electron-phonon interactions in MgB2 through detailed Raman scattering analysis.

Findings

Anharmonic two phonon decay causes large linewidth of E2g mode.

E2g phonon frequency hardens by ~2.5% below superconducting transition.

Estimated electron-phonon coupling strength from phonon renormalization.

Abstract

We present a Raman scattering study of the E2g phonon anharmonicity and of superconductivity induced self-energy effects in MgB2 single crystals. We show that anharmonic two phonon decay is mainly responsible for the unusually large linewidth of the E2g mode. We observe ~ 2.5 % hardening of the E2g phonon frequency upon cooling into the superconducting state and estimate the electron-phonon coupling strength associated with this renormalization.