Pressure dependence of the single particle excitation in the charge-density-wave ${\text{CeTe}}_3$ system

We present data on the pressure dependence at 300 K of the optical reflectivity of ${\text{CeTe}}_3$, which undergoes a charge-density-wave (CDW) phase transition well above room temperature. The collected data cover an unprecedented broad spectral range from the infrared up to the ultraviolet, which allows a robust determination of the gap as well as of the fraction of the Fermi surface affected by the formation of the CDW condensate. Upon compressing the lattice there is a progressive closing of the gap, inducing a transfer of spectral weight from the gap feature into the Drude component. At frequencies above the CDW gap we also identify a power-law behavior, consistent with findings along the $R{\text{Te}}_3$ series (i.e., chemical pressure) and suggestive of a Tomonaga-Luttinger liquid scenario at high-energy scales. This set of data is placed in the context of our previous investigations of this class of materials and allows us to revisit important concepts for the physics of CDW state in layeredlike two-dimensional systems.

Figure 1

(Color online) (a) The reflectivity $R\left(\omega \right)$ of ${\text{CeTe}}_3$ at 300 K as a function of pressure and (b) the real part ${\sigma }_1\left(\omega \right)$ of the optical conductivity (see text). The arrow in panel (a) indicates the $R\left(\omega \right)$ trend upon increasing pressure.

Figure 2

(Color online) Reflectivity ratio $R\left(\omega ,p\right)/R\left(\omega ,p_{\text{max}}\right)$ at 300 K for (a) ${\text{CeTe}}_3$ and for (b) ${\text{NdTe}}_3$. $p_{\text{max}}$ corresponds to the maximal pressures of 7.6 and 9 GPa reached in our experiment for ${\text{CeTe}}_3$ and ${\text{NdTe}}_3$, respectively. The arrow in panel (a) indicates the $R\left(\omega \right)$ trend upon increasing pressure.

Figure 3

(Color online) (a) Measured $R\left(\omega \right)$ of ${\text{CeTe}}_3$ at 0.7 GPa and its extension based on the LD fit (see text). (b) Real part ${\sigma }_1\left(\omega \right)$ of the complex optical conductivity achieved through KK transformation of the spectrum in panel (a) and its reproduction within the Lorentz-Drude fit. The fit components are displayed, as well. The dashed vertical lines in panel (b) highlight the spectral range, where the original $R\left(\omega \right)$ data were collected.

Figure 4

(Color online) The ratio $\Phi$ [Eq. (3)] versus the single particle peak ${\omega }_{\text{SP}}$ [Eq. (2)] for the experiment on ${\text{CeTe}}_3$ under externally applied pressure and for the data collected on the $R{\text{Te}}_3$ series (i.e., chemical pressure) (Ref. 15).

Figure 5

(Color online) ${\sigma }_1\left(\omega \right)$ of ${\text{CeTe}}_3$ at selected pressures plotted on a bilogarithmic scale. The $y$-axis is scaled by the maximum of the midinfrared peak in ${\sigma }_1$, while the energy axis is scaled by the frequency $\left({\omega }_{\text{max}}\right)$ where the maximum in ${\sigma }_1\left(\omega \right)$ occurs. The solid lines are power-law $\left[{\sigma }_1\left(\omega \right)\sim {\omega }^{-\eta }\right]$ fits to the data. The pressure dependence of the exponent $\eta$ is summarized in the inset (Ref. 33), as well as in Table .