Pressure-induced quenching of the charge-density-wave state in rare-earth tritellurides observed by x-ray diffraction

We report an x-ray diffraction study on the charge-density-wave (CDW) ${\text{LaTe}}_3$ and ${\text{CeTe}}_3$ compounds as a function of pressure. We extract the lattice constants and the CDW modulation wave vector. We observe that the intensity of the CDW satellite peaks tend to zero with increasing pressure, thus providing direct evidence for a pressure-induced quenching of the CDW phase. Our findings further support the equivalence between chemical and applied pressures in $R{\text{Te}}_3$, put forward by our previous optical investigations, but reveal some subtle differences. We offer a possible explanation for these differences.

Figure 1

(Color online) Selected XRD patterns on single-crystals of ${\text{LaTe}}_3$ at 300 K and at (a) 0.3 GPa and (b) 5.1 GPa, and of ${\text{CeTe}}_3$ at 300 K and at (c) 0.7 GPa and (d) 3.0 GPa, and finally on polycrystalline ${\text{LaTe}}_3$ at 270 K and (e) 6.2 GPa, and at 30 K and (f) 5.9 GPa. Circles highlight the CDW satellite peaks. The modulation vector $\vec{q}$ is also shown in (a).

Figure 2

(Color online) Lattice parameters (left panels) and unit-cell volume (right panels) for ${\text{CeTe}}_3$ at 300 K [(a) and (b)] as a function of pressure and for ${\text{LaTe}}_3$ polycrystal at $6.0\pm 0.2\text{GPa}$ [(c) and (d)] as a function of temperature. The solid line in (b) is the Birch-Murnaghan fit to the data (Ref. 18). Vertical dashed lines indicate the pressure and temperature where the CDW satellite peaks (Fig. 1) disappear.

Figure 3

(Color online) Intensity of selected CDW satellite peaks normalized to a nearby Bragg-peak for (a) ${\text{LaTe}}_3$ and (b) ${\text{CeTe}}_3$ at 300 K as a function of pressure and for ${\text{LaTe}}_3$ at $6.0\pm 0.2\text{GPa}$ as a function of temperature, with the prediction from the BCS theory (c). (d) Ratio $b/\tilde{a}$ (see text) as a function of the average lattice constant $\tilde{a}$. Thin lines in panel (d) are linear interpolations to the data, as guide to the eyes.

Figure 4

(Color online) (a) Magnitude of the CDW wave vector $\vec{q}$ and (b) of the CDW gap $2\Delta$ at 300 K for the $R{\text{Te}}_3$ series and for ${\text{LaTe}}_3$ and ${\text{CeTe}}_3$ under applied pressure as a function of the average lattice constant $\tilde{a}$ (see text), respectively. Chemical-pressure data in (a) are from Ref. 8 and the $2\Delta$ values in (b) are from Refs. 10, 12 for $R{\text{Te}}_3$ and ${\text{CeTe}}_3$, respectively. (c) CDW-transition temperature $T_{\text{CDW}}$ as a function of $\tilde{a}$ for the $R{\text{Te}}_3$ series[8, 9] and for ${\text{LaTe}}_3$ and ${\text{CeTe}}_3$ at high pressures. The solid and dashed lines in (c) are linear fits to the data.