A minimal, "hydrogen atom" version of an inversion-breaking Weyl semimetal

Abstract

The recent explosion of research interest in Weyl semimetals has led to many proposed Weyl semimetal candidates and a few experimental observations of a Weyl semimetal in real materials. Through this experience, we have come to appreciate that typical Weyl semimetals host many Weyl points. For instance, the first Weyl semimetal observed in experiment, TaAs, hosts 24 Weyl points. Similarly, the Mo${}_x$W${}_{1-x}$Te${}_2$ series, recently under study as the first Type II Weyl semimetal, has eight Weyl points. However, it is well-understood that for a Weyl semimetal without inversion symmetry but with time-reversal symmetry, the minimum number of Weyl points is four. Realizing such a minimal Weyl semimetal is fundamentally relevant because it would offer the simplest "hydrogen atom" example of an inversion-breaking Weyl semimetal. At the same time, transport experiments and device applications may be simpler in a system with as few Weyl points as possible. Recently, TaIrTe${}_4$ has been predicted to be a minimal, inversion-breaking Weyl semimetal. However, crucially, the Weyl points and Fermi arcs live entirely above the Fermi level, making them inaccessible to conventional angle-resolved photoemission spectroscopy (ARPES). Here we use pump-probe ARPES to directly access the band structure above the Fermi level in TaIrTe${}_4$. We directly observe Weyl points and topological Fermi arcs, showing that TaIrTe${}_4$ is a Weyl semimetal. We find that, in total, TaIrTe${}_4$ has four Weyl points, providing the first example of a minimal inversion-breaking Weyl semimetal. Our results hold promise for accessing exotic transport phenomena arising in Weyl semimetals in a real material.

References in corpus (9)

• Maximally-localized generalized Wannier functions for composite energy bands
• Type-II Weyl Semimetals
• Experimental observation of topological Fermi arcs in type-II Weyl semimetal MoTe2
• Prediction of the Weyl semimetal in the orthorhombic MoTe2
• MoTe2: A Type-II Weyl Topological Metal
• Arc-tunable Weyl Fermion metallic state in Mo${}_x$W${}_{1-x}$Te${}_2$
• Fermi arcs and their topological character in the candidate type-II Weyl semimetal MoTe2
• Criteria for directly detecting topological Fermi arcs in Weyl semimetals
• Measuring Chern numbers above the Fermi level in the Type II Weyl semimetal Mo${}_x$W${}_{1-x}$Te${}_2$

Cited by in corpus (5)

• Weyl and Dirac Semimetals in Three Dimensional Solids
• Raman Signatures of Broken Inversion Symmetry and In-plane Anisotropy in Type-II Weyl Semimetal Candidate TaIrTe4
• Weyl Josephson Circuits
• Triple point fermions in a minimal symmorphic model
• Discovery of magnetic topological crystals