Figure 3: Simulation and experimental results show combination and overtone modes.
From: The origin of incipient ferroelectricity in lead telluride
(a) Simulated FT-IXS spectrum along the Δ line in the (1 3) BZ. The 2TA and TO±TA modes are labelled. The spectrum qualitatively matches the experimental data in b. (b) Experimental FT-IXS spectrum along the same high-symmetry direction in the (1 3) BZ seen in Fig. 2b and with the slowly varying low frequency background filtered. (c) Comparison of experimental time-domain signal (black traces, unfiltered) at select wavevector coordinates along Δ as taken from Fig. 2a with calculated signal (orange traces). There is a good qualitative match between experimental and model results, notably in the strong initial dip seen at τ=0, connected to a considerable hardening of the TO branch frequencies.
