8 research outputs found
Precursor phase with full phonon softening above the charge-density-wave phase transition in -TaSe
Research on charge-density-wave (CDW) ordered transition-metal
dichalcogenides continues to unravel new states of quantum matter correlated to
the intertwined lattice and electronic degrees of freedom. Here, we report an
inelastic x-ray scattering investigation of the lattice dynamics of the
canonical CDW compound -TaSe complemented by angle-resolved
photoemission spectroscopy. Our results rule out the central-peak scenario for
the CDW transition in -TaSe and provide evidence for a novel precursor
phase above the CDW transition temperature . The phase at temperatures
between and is
characterized by a fully softened phonon mode and medium-range ordered
( static CDW
domains. Only is detectable in our photoemission experiments. Thus,
-TaSe exhibits structural before electronic static order and emphasizes
the important lattice contribution to CDW transitions
Precursor region with full phonon softening above the charge-density-wave phase transition in 2H-TaSe2
Research on charge-density-wave (CDW) ordered transition-metal dichalcogenides continues to unravel new states of quantum matter correlated to the intertwined lattice and electronic degrees of freedom. Here, we report an inelastic x-ray scattering investigation of the lattice dynamics of the canonical CDW compound 2H-TaSe2 complemented by angle-resolved photoemission spectroscopy and density functional perturbation theory. Our results rule out the formation of a central-peak without full phonon softening for the CDW transition in 2H-TaSe2 and provide evidence for a novel precursor region above the CDW transition temperature TCDW, which is characterized by an overdamped phonon mode and not detectable in our photoemission experiments. Thus, 2H-TaSe2 exhibits structural before electronic static order and emphasizes the important lattice contribution to CDW transitions. Our ab-initio calculations explain the interplay of electron-phonon coupling and Fermi surface topology triggering the CDW phase transition and predict that the CDW soft phonon mode promotes emergent superconductivity near the pressure-driven CDW quantum critical point