Multiple charge density wave ordering and quantum coupling of collective excitations in layered GdTe3

Rare-earth tritellurides represent quasi-two-dimensional systems that exhibit multiple charge density wave (CDW) transitions alongside magnetic ordering. However, the interplay between the phonon dynamics of collective excitations and local magnetism remains unclear. GdTe₃ is an interesting material having an incommensurate CDW (ICDW), at TICDW~380 K, an antiferromagnetic transition at TN~13 K, and with an expectation of another CDW ordering. We emphasize electron-spin-phonon and mode coupling in GdTe₃ through temperature dependent Raman spectroscopy complemented by heat capacity and magnetization measurements. Disappearance of zone-folded mode (Z*) and observed coupling behavior of amplitude mode suggest the existence of another ordering at ~240 K, in addition to known ICDW. By employing phonon renormalization, we estimated significant strength of spin-phonon coupling, (λ_s-ph~0.234) and accentuated on the phonon dynamics associated with CDW instabilities in GdTe₃.