Comment on: "Coherent perfect absorption: Zero reflection without linewidth suppression"

Abstract

A recent paper, Phys. Rev. Research 8, 013261 (2026), claims that the polaromechanical normal-mode splitting (NMS) measured in Nat. Commun. 16, 5652 (2025) is not true based on their two results: $i$) there is no true splitting in the linear-scale spectrum; $ii$) the total or intrinsic decay rate of the cavity-magnon polariton, set by the imaginary part of the pole of the total output spectrum, remains unchanged under the coherent-perfect-absorption (CPA) condition. In this comment, we indicate that $i$) there is NMS in both the linear and logarithmic scales of our spectra in {\it a narrow frequency range} around the CPA frequency; $ii$) the total decay rate defined via the {\it pole} of the spectrum cannot characterize the vanishing {\it effective} decay rate at the CPA frequency (known as the monochromaticity of the CPA), and thus this parameter is irrelevant to the NMS measured in our experiment in {\it a narrow frequency range} around the CPA frequency. Consequently, their results above are either false or irrelevant, and thus cannot support their claim on the polaromechanical strong coupling measured in our experiment.

Figures (1)

• Figure 1: (a) Fig. 3b of Ref. Shen. (b) Logarithmic scale and (d) linear scale of the data of Fig. 4a in Ref. Shen. In the linear scale (d), the NMS is not clearly visible because the values of the red-shaded area in the bottom graph of (a), from 10.9458 to 10.9558 MHz, are several orders of magnitude larger than those in the rest part, which causes almost the entire area to be dark. However, the hidden NMS in (d) emerges when the data of the red-shaded area are not presented, yielding the blank area in (e). The same operation turns the logarithmic-scale (b) into (c). In (e), the two branches of the white dots (measured data) denote the frequency shift of the two dips in (a), which clearly shows the splitting.