Fig. 4.

Characterization of the IR limit. (A) Ratio $\pi {\mathrm{\Gamma }}_{T_2}/\mathrm{\Omega }$ for the T₂ excitations, calculated from the data of Fig. 3, at the indicated values of λ. The frequency corresponding to the intersection of each dataset with the horizontal line at the value 1 defines the IR limit, ${\mathrm{\Omega }}_{T_2}^{\text{IR}}$. (B) λ dependence of ${\mathrm{\Omega }}_{T_2}^{\text{IR}}$ extracted from the above data, corresponding to the T₂ branch. We also show ${\mathrm{\Omega }}_L^{\text{IR}}$ and ${\mathrm{\Omega }}_{T_1}^{\text{IR}}$ for the longitudinal (L) and higher transverse (T₁) branches, respectively. The vertical line indicates the transition point λ* ≃ 0.81. The horizontal line corresponds to the BP position, Ω^BP ≃ 1, for the amorphous phases at λ ≤ 0.78.