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arXiv · 2608.14882

Higher-order nonadiabaticity governs the temperature dependence of the phonon spectrum

Nina Girotto Erhardt·Samuel Poncé
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Abstract

Nonadiabatic effects determine the frequency and linewidth of coupled phonon modes, shape of Kohn anomalies and have important implications on many material properties. State-of-the-art ab-initio nonadiabatic phonon self-energy relies on an infinite electron lifetime approximation, which cannot capture the temperature dependence of the phonon spectrum, neglects long-wavelength intraband phonon decay, and exhibits exaggerated phonon splitting. In MgB$_2$, we show how the higher-order nonadiabatic phonon corrections mitigate these deficiencies, yielding linewidths in a closer experimental agreement and a dome-like coupling strength temperature dependence.

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Nina Girotto Erhardt, Samuel Poncé. 2026-08-14. Higher-order nonadiabaticity governs the temperature dependence of the phonon spectrum. https://arxiv.org/abs/2608.14882

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