Abstract
We present optical measurements of the transition metal dichalcogenide . The reflectivity displays an unusual temperature and energy dependence in the far infrared, which we show can only be explained by a collapse of the scattering rate at low temperature, resulting from the vicinity of a van Hove singularity near the Fermi energy. An analysis of the optical conductivity suggests that below 150 K a reduction in the available phase space for scattering takes place, resulting in long-lived quasiparticle excitations. We suggest that this reduction in phase space provides experimental evidence for a van Hove singularity close to the Fermi level. Our data furthermore indicates a very weak electron-phonon coupling. Combined this suggests that the superconducting transition temperature is set by the density of states associated with the van Hove singularity.
- Received 14 June 2019
- Revised 25 August 2019
DOI:https://doi.org/10.1103/PhysRevMaterials.3.114202
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