Chemical pressure and hidden one-dimensional behavior in rare-earth tri-telluride charge-density wave compounds

Abstract

We report on the first optical measurements of the rare-earth tri-telluride charge-density wave systems. Our data, collected over an extremely broad spectral range, allow us to observe both the Drude component and the single-particle peak, ascribed to the contributions due to the free charge carriers and to the charge-density wave gap excitation, respectively. The data analysis displays a diminishing impact of the charge-density wave condensate on the electronic properties with decreasing lattice constant across the rare-earth series. We propose a possible mechanism describing this behavior and we suggest the presence of a one-dimensional character in these two-dimensional compounds. We also envisage that interactions and umklapp processes might play a relevant role in the formation of the charge-density wave state in these compounds.

Pressure suppression of unconventional charge-density-wave state in PrRu4P12studied by optical conductivity

“…[35][36][37] A peak was commonly observed in their σ(ω) spectra, whose energy was identified as the CDW gap magnitude. The peak shifted to lower energy, and hence the CDW gap decreased, with lattice contraction given by different R elements 34,35 and also by external pressure. [35][36][37] In contrast, as already mentioned, the gap excitation peak of PrRu 4 P 12 decreases only slightly with P .…”

“…Such a concept has been applied to analyze the optical data of the RTe 3 compounds. [34][35][36][37] In the case of RTe 3 with layered crystal structure, the CDW had a strong 2D character, driven by a 2D nesting of FS. As a result, the FS nesting was not complete and only a part of FS was gapped.…”

“…To determine the position of the gap excitation peak and its shifts with P , we adapted a previously reported method used to analyze a CDW gap. [34][35][36][37] Namely, the center-of-mass energy (ω CM ) of the three Lorentz oscillators used in the fitting, defined as ω CM = i ω 0,i S i / i S i where i denotes L1, L2, and L3, was regarded as the peak position. As shown in Fig.…”

Optical properties of the Ce and La ditelluride charge density wave compounds

“…RTe 2 share several common features and similar properties with the related bilayer RTe 3 materials [11]. The structural and electronic simplicity of RTe 2 and RTe 3 , combined with the large size of the CDW gap, makes these materials particularly attractive for studying the effect of CDW formation on the electronic structure of layered systems.…”

“…One approach is to exploit optical spectroscopy methods, which are ideal experimental tools to get insight into the absorption spectrum of the investigated materials. Optical data allow in principle to address both the gapped as well as the ungapped fractions of FS [11]. We seek to identify and to discuss the gap excitation and the fraction of FS involved in the CDW transition.…”