Observation of a van Hove singularity of a surface Fermi arc with prominent coupling to phonons in a Weyl semimetal

A van der Waals coupled Weyl semimetal ${\mathrm{NbIrTe}}_{4}$ is investigated by combining scanning tunneling microscopy/spectroscopy and first-principles calculations. We observe a sharp peak in the conductance near Fermi energy (${E}_{F}$). Comparison with calculations indicates that originates from Hove singularity (vHs) associated Lifshitz transition of surface Fermi-arc state. Interestingly, our spectroscopy also shows signatures strong electron-boson coupling. This potentially due to an anomalously enhanced charge susceptibility coming near-${E}_{F}$ vHs formation.