General ab initio framework for electronic-order-induced lattice-dynamics symmetry breaking
Abstract
Conventional ab initio approaches are unable to describe phonon time-reversal symmetry (T) breaking. Here, we develop an ab initio framework, grounded in molecular Berry curvature (MBC) theory, that captures electronic-order-driven symmetry breaking in lattice dynamics. Using Co3Sn2S2 as a model system, our ab initio framework yields phonon spectra that break both T and mirror symmetries, quantitatively reproduce the observed phonon splittings observed in experiments, and reveal distinct microscopic origins for the Eg and Eu modes: Eg splitting is governed by MBC and is accurately captured by our algorithm, whereas Eu splitting is enhanced by the Fano resonance and matches the experimental data once the Fano-factor correction is included. Leveraging this algorithm, we predict several candidate materials with nonzero electronic-order-driven symmetry breaking in lattice dynamics, establishing a first-principles route to understand electron-phonon coupling, phonon magnetism, and related Hall-type lattice responses.
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