Observation of near EF Fermi-arc van Hove singularity with prominent coupling to phonon in a van der Waals coupled Weyl semimetal

TL;DR

This study identifies a van Hove singularity near the Fermi level in a van der Waals Weyl semimetal, revealing strong electron-phonon coupling and potential for nanoscale topological device applications.

Contribution

It reports the first observation of a van Hove singularity linked to Fermi arc Lifshitz transition in a van der Waals Weyl semimetal, with evidence of enhanced electron-phonon interactions.

Findings

Sharp tunneling conductance peak near zero bias

Van Hove singularity associated with Lifshitz transition

Enhanced electron-phonon coupling observed

Abstract

A van der Waals coupled Weyl semimetal material NbIrTe4 is investigated by combining scanning tunneling microscopy/spectroscopy and first principles calculations. We observe a sharp peak in the tunneling conductance near the zero bias energy, and its origin is ascribed to a van Hove singularity associated with a Lifshitz transition of the topologically none trivial Fermi arc states. Furthermore, tunneling spectroscopy measurements show a surprisingly large signature of electron boson coupling, which presumably represents anomalously enhanced electron phonon coupling through the enhanced charge susceptibility. Our finding in van der Waals coupled material is particularly invaluable due to applicable exfoliation technology for searching exotic topological states by further manipulating near Fermi energy van Hove singularity in nanometer scale flakes and their devices.