Nearly quantized Born effective charges as probes for the topological phase transition in the Haldane and Kane-Mele models

The authors introduce here a novel method for examining transitions between distinct topological phases by analyzing vibrational resonances in infrared spectra. In the prototypical Haldane and Kane-Mele models, the Born effective charges, which measure the interaction between infrared light and phonons, are nearly quantized and exhibit a sharp change that coincides with the topological phase transition. In the Haldane model, which breaks time-reversal symmetry, a similar discontinuous shift is also observed in the chiral phonon splitting.