(a) Absorbance spectra at selected pressure values over the range [1 ÷ 19] GPa. (b) Normalized spectral weight SW (P, P0) (see text); the red vertical stripe highlights the pressure range where the change of slope occurs.

Contexts in source publication

Context 1

... better characterize the pressure response of the Drude contribution in the sample absorbance, we collected A(ω) spectra in the FIR region over the [1÷19] GPa range, see Fig. 2(a). At every pressure, both I 0 (ω) and I(ω) exhibit intense oscillations, clearly visible also in the corresponding A(ω) curve. In this case, measurements were collected in the inter-band energy region where the MoTe 2 is largely transparent and the interference fringes are compatible with multiple reflections between the diamond inner ...

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... phonon peak also shows a clear broadening and a frequency hardening on increasing pressure, an effect that will be discussed in detail in the next section. Focusing on the overall trend of the spectra in Fig. 2(a), it can be noticed that they remain almost overlapped at low pressures (approximately over 0÷13 GPa), while their intensities rapidly rise on further increasing pressure. A simple application of the Drude model proves that in the low-frequency limit, i.e. ω/Γ 1 with Γ = c/τ and τ the Drude relaxation time, the experimental absorbance ...

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... then conveniently introduce the normalized quantity SW (P, P 0 ) = sw(P )/sw(P 0 ), which describes the variation of the spectral weight from the minimum pressure value P 0 =1 GPa. In Fig. 2(b) we show the SW (P, P 0 ) values obtained with ω m =100 cm −1 and ω M =600 cm −1 . The integration does not include the 200÷270 cm −1 range where the phonon contribution is dominant. Our results indicate the onset of a phase with metallic characteristics between 13÷15 GPa, in good agreement with previous resistivity measurements ...

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... in good agreement with previous resistivity measurements [13,15]. This finding is also consistent with the onset of the low-frequency contribution (Drude peak), as discussed in the previous section. We want to finally notice that the spectral weight analysis is a robust procedure as the same trend of the spectral weight function with pressure ( Fig. 2(b)) is obtained either non excluding the phonon frequency region or varying the integration limits ω m and ω M (data not ...

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... mentioned, FIR absorption spectra exhibit an intense phonon peak at 235 cm −1 attributed to the E 1u vibrational mode. The inspection of the raw spectroscopic data shown in Fig. 2(a) reveals that the E 1u peak presents an unusual asymmetric shape in the low pressure regime, and it is notably affected by pressure. To rule out the effect of the diamond-diamond interference fringes on the line shape asymmetry, a further absorption measurement was carried out on a simple MoTe 2 slab kept out of the DAC (that is at P=0 ...