The presence of a quantum-critical point at which a nearby ordered phase is suppressed to zero temperature is often invoked to explain emergent quantum phases, e.g. superconductivity. Yet, identifying a quantum critical point and establishing its correlation with superconductivity remains challenging. Materials featuring charge-density-wave (CDW) order and superconductivity seem to offer a clear scenario as both states can be associated with electron-phonon coupling.

Here, I will present an inelastic X-ray scattering (IXS) and X-ray diffraction (XRD) investigation focusing of the charge-density-wave state in 2H-TaSe₂ at ambient and hydrostatic pressure of up to 25 GPa complemented by ab-initio lattice dynamical calculations. Our ambient-pressure IXS results provide evidence for a novel precursor region above the CDW transition temperature T_CDW, which is characterized by an overdamped phonon mode without long-range CDW order [1]. We determined the evolution of the charge-density-wave state and its lattice dynamics up to and beyond its suppression at the critical pressure p_c = 19.9(1) GPa. We find the pressure-induced CDW quantum critical point in close vicinity to the maximum superconducting transition temperature and ab-initio lattice dynamical calculations corroborate that 2H-TaSe₂ is a reference example for order-suppressed enhanced superconductivity that can serve as a paradigm to investigate superconductivity near a CDW quantum critical point.

[1] Shen et al. Nat Commun 14, 7282 (2023), https://doi.org/10.1038/s41467-023-43094-5

[2] Tymoshenko et al. Communications Physics 8, 352 (2025), https://doi.org/10.1038/s42005-025-02254-3