Fig. 1
From: Signatures of a time-reversal symmetric Weyl semimetal with only four Weyl points
Constraints on Weyl points in \({\cal T}\) symmetric systems. a Illustration of the minimal number of Weyl points in a \({\cal T}\) invariant Weyl semimetal. The blue and red circles and cones represent Weyl points and Weyl cones with ±1 chiral charge at generic k-points. In a \({\cal T}\) invariant Weyl semimetal, the minimal number of Weyl points is four because \({\cal T}\) symmetry sends a Weyl point of a given chiral charge at k to a Weyl point of the same chiral charge at −k (orange arrow). To preserve net zero chiral charge, four Weyl points are needed. b The crystal structure of TaIrTe4 is layered, in space group 31, which breaks inversion symmetry. c The bulk Brillouin zone (BZ) and (001) surface BZ of TaIrTe4 with high-symmetry points marked in red. d The electronic band structure of TaIrTe4 along high-symmetry lines. There is a band crossing in the region near Γ, with Weyl points off Γ − S (blue box). e Cartoon illustration of the constant-energy contour at E B = E W and k z = 0, with bulk electron and hole pockets which intersect to form Weyl points. A detailed calculation shows that there are in total four Type II Weyl points (blue and red circles)27. f Energy-dispersion calculation along a pair of Weyl points in the k y direction, marked by the orange line in e. The Weyl points and Fermi arcs live at ~0.1 eV above E F, requiring the use of pump-probe ARPES to directly access the unoccupied band structure to demonstrate a Weyl semimetal
