Comment on "Collective modes and gapped momentum states in liquid Ga: Experiment, theory, and simulation"

TL;DR

This paper critically examines a previous theoretical work on liquid gallium, demonstrating that its expressions for spectral functions and excitation dispersions are incorrect and incompatible with fundamental physical principles.

Contribution

The authors identify and clarify errors in the prior theoretical expressions for collective modes in liquid gallium, emphasizing the importance of consistency with the continuum limit and continuity equation.

Findings

Previous theoretical expressions are incompatible with the continuum limit.

The spectral function $C^L(k,)$ contradicts the continuity equation.

Corrected theoretical framework is necessary for accurate description.

Abstract

We show that the presented in Phys.Rev.B, v.101, 214312 (2020) theoretical expressions for longitudinal current spectral function $C^L(k,\omega)$ and dispersion of collective excitations are not correct. Indeed, they are not compatible with the continuum limit and $C^L(k,\omega\to 0)$ contradicts the continuity equation.