Abstract
Through intense research on Weyl semimetals during the past few years, we have come to appreciate that typical Weyl semimetals host many Weyl points. Nonetheless, the minimum nonzero number of Weyl points allowed in a time-reversal invariant Weyl semimetal is four. Realizing such a system is of fundamental interest and may simplify transport experiments. Recently, it was predicted that TaIrTe4 realizes a minimal Weyl semimetal. However, 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 TaIrTe4. We observe signatures of Weyl points and topological Fermi arcs. Combined with ab initio calculation, our results show that TaIrTe4 is a Weyl semimetal with the minimum number of four Weyl points. Our work provides a simpler platform for accessing exotic transport phenomena arising in Weyl semimetals.
Highlights
Through intense research on Weyl semimetals during the past few years, we have come to appreciate that typical Weyl semimetals host many Weyl points
One crucial challenge is that the Weyl points and topological Fermi arcs are predicted to live entirely above the Fermi level in TaIrTe4, so that they are inaccessible to conventional angle-resolved photoemission spectroscopy (ARPES)
If an I breaking Weyl semimetal has no additional symmetries which produce copies of Weyl points, the minimum number of Weyl points is fixed by T symmetry and the requirement that total chiral charge vanish
Summary
Through intense research on Weyl semimetals during the past few years, we have come to appreciate that typical Weyl semimetals host many Weyl points. The minimum nonzero number of Weyl points allowed in a time-reversal invariant Weyl semimetal is four Realizing such a system is of fundamental interest and may simplify transport experiments. The first Weyl semimetals observed in experiment, TaAs and its isoelectronic cousins, have an I breaking crystal structure, which gives rise to a band structure hosting 24 Weyl points distributed throughout the bulk Brillouin zone[10,11,12,13,14,15,16,17]. One crucial challenge is that the Weyl points and topological Fermi arcs are predicted to live entirely above the Fermi level in TaIrTe4, so that they are inaccessible to conventional angle-resolved photoemission spectroscopy (ARPES). We observe signatures of Weyl points and topological Fermi arcs in TaIrTe4, realizing the first minimal T invariant Weyl semimetal. We conclude that TaIrTe4 can be viewed as a minimal Weyl semimetal, with the simplest configuration of Weyl points allowed in a T invariant crystal
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