| Rare earth (R) telluride compounds have attracted recent attention due to their effective low dimensionality. RTen (n=2, 2.5, 3) play host to a charge density wave (CDW) and can be described in terms of a nominally tetragonal structure based on alternating layers of square-planar Te sheets and a corrugated RTe slab (R=Rare Earth). Band structure calculations for the material indicate a strongly anisotropic two dimensional Fermi surface (FS) of mostly Te 5p character with minimal dispersion perpendicular to the Te planes, and a superlattice modulation of the average structure has been observed, which can be understood in terms of optimal nesting of a Fermi surface derived from simple tight-binding arguments. These observations essentially establish the lattice modulation in these materials as a charge density wave (CDW), driven by an electronic instability of the Fermi surface. The structural and electronic simplicity, combined with the large size of the CDW gap, makes these materials particularly attractive for studying CDW formation and its effect on the electronic and crystal structure.;In this study, the results of TEM, high resolution X-ray Diffraction, heat capacity and resistivity measurements of single crystals of two specific families of layered rare earth tellurides, RTe2 (R=La and Ce) and R2Te5 (R=Nd, Sm and Gd) are reported. We have prepared high quality samples in single crystal form using an alternative self-flux technique, which lends itself to minimizing the risk of contamination by not using a separate flux or transport agent. The CDW in R2Te5 ( R=Nd, Sm and Gd) was first observed in this study and the measurements provide complementary information about the competing CDW order parameters formed in different Te layers in the crystal. Each of the materials exhibits a complex mixture of incommensurate and commensurate CDW vectors and the origin of the observations are discussed in terms of the electronic structure and the susceptibility. Our results indicate that subtle differences, such as the choice of rare earth and band filling, can substantially affect the superlattice modulation and electronic structure. |
