Observation of symmetry-protected Dirac states in nonsymmorphic <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>?</mml:mi></mml:math> -antimonene

Two-dimensional (2D) Dirac states with linear band dispersion have attracted enormous interest since the discovery of graphene. However, to date, 2D semimetals are still very rare due fact that generally fragile against perturbations such as spin-orbit couplings. Nonsymmorphic crystal symmetries can enforce formation nodes, providing a new route establishing symmetry-protected in materials. Here we report nonsymmorphic alpha-antimonene. The antimonene was synthesized by method molecular beam epitaxy. Two cones large anisotropy were observed angle-resolved photoemission spectroscopy. state alpha-antimonene is type contrast spinless result extends 'graphene' physics into family materials where coupling present.