Experimental realization of type-II Weyl state in non-centrosymmetric TaIrTe$_4$

TL;DR

This paper reports the experimental discovery of a type-II Weyl semimetal state in non-centrosymmetric TaIrTe$_4$, providing clear evidence of Fermi arcs and spin-polarized surface states, advancing the understanding of topological quantum materials.

Contribution

The study provides the first direct experimental observation of type-II Weyl states in TaIrTe$_4$, confirming theoretical predictions and revealing spin-polarized Fermi arcs.

Findings

Observation of quasi-1D Fermi arcs connecting four Weyl points

Direct ARPES spectra match theoretical electronic structure

Surface states are spin-polarized along the arcs

Abstract

Recent breakthrough in search for the analogs of fundamental particles in condensed matter systems lead to experimental realizations of 3D Dirac and Weyl semimetals. Weyl state can be hosted either by non-centrosymmetric or magnetic materials and can be of the first or the second type. Several non-centrosymmetric materials have been proposed to be type-II Weyl semimetals, but in all of them the Fermi arcs between projections of multiple Weyl points either have not been observed directly or they were hardly distinguishable from the trivial surface states which significantly hinders the practical application of these materials. Here we present experimental evidence for type-II non-centrosymmetric Weyl state in TaIrTe$_4$ where it has been predicted theoretically. We find direct correspondence between ARPES spectra and calculated electronic structure both in the bulk and the surface and clearly observe the exotic surface states which support the quasi-1D Fermi arcs connecting only four Weyl points. Remarkably, these electronic states are spin-polarized in the direction along the arcs, thus highlighting TaIrTe$_4$ as a novel material with promising application potential.