Lattice Instability Induced Concerted Structural Distortion in Charged and van der Waals Layered GdTe3

Abstract Structural mosaic of rare‐earth tri‐tellurides (RTe 3 ) inlaid with non‐classical structural motifs like the 2D−polytelluride square nets has attracted immense attention owing to their enigmatic chemical bonding, unconventional structure, and harboring charge density wave (CDW) ground states. GdTe 3 , an archetypal RTe 3 , is a natural heterostructure of charged and van der Waals (vdW) layers, formed by intercalating vdW gap separated 2D square telluride nets [(Te 2 ) − ] n between the charged double corrugated slabs of n [GdTe] + . Here, we have investigated the evolution of structural distortions along with the electrical and thermal transport properties of GdTe 3 across its CDW transition through X‐ray pair distribution function analysis, thermal conductivity measurements, Raman spectroscopy and first principles theoretical calculations. The results reveal that the unusual structure of GdTe 3 engenders a large anisotropic lattice thermal conductivity by concomitantly hampering the phonon propagation along parallel to the spark plasma sintering (SPS) pressing direction via chemical bonding hierarchy while facilitating phonon propagation along perpendicular to the SPS pressing direction through the metallic Te sheets and phason channel. The low lattice thermal conductivity is attributed to the strong vibrational anharmonicity caused by CDW‐induced concerted local lattice distortions of both Gd–Te slab and Te square net, and the robust electron–phonon coupling.