biostudies-literatureLe CEuropean Research Council8311-8315https://www.ebi.ac.uk/biostudies/studies/S-EPMC6099897biostudies-literatureUnknown115(33)Anomalous surface states with Fermi arcs are commonly considered to be a fingerprint of Dirac semimetals (DSMs). In contrast to Weyl semimetals, however, Fermi arcs of DSMs are not topologically protected. Using first-principles calculations, we predict that β-cuprous iodide (β-CuI) is a peculiar DSM whose surface states form closed Fermi pockets instead of Fermi arcs. In such a fermiological Dirac semimetal, the deformation mechanism from Fermi arcs to Fermi pockets stems from a large cubic term preserving all crystal symmetries and from the small energy difference between the surface and bulk Dirac points. The cubic term in β-CuI, usually negligible in prototypical DSMs, becomes relevant because of the particular crystal structure. As such, we establish a concrete material example manifesting the lack of topological protection for surface Fermi arcs in DSMs.Proceedings of the National Academy of Sciences of the United States of AmericaDirac semimetal in <i>β</i>-CuI without surface Fermi arcs.PMC6099897336012Li YZhang FCHu JThomale RLe CWu XQin SfalseDirac semimetal in <i>β</i>-CuI without surface Fermi arcs.Anomalous surface states with Fermi arcs are commonly considered to be a fingerprint of Dirac semimetals (DSMs). In contrast to Weyl semimetals, however, Fermi arcs of DSMs are not topologically protected. Using first-principles calculations, we predict that β-cuprous iodide (β-CuI) is a peculiar DSM whose surface states form closed Fermi pockets instead of Fermi arcs. In such a fermiological Dirac semimetal, the deformation mechanism from Fermi arcs to Fermi pockets stems from a large cubic term preserving all crystal symmetries and from the small energy difference between the surface and bulk Dirac points. The cubic term in β-CuI, usually negligible in prototypical DSMs, becomes relevant because of the particular crystal structure. As such, we establish a concrete material example manifesting the lack of topological protection for surface Fermi arcs in DSMs.2018-01-01T00:00:00Z2018 Aug2026-05-06T06:44:57.517Z2025-05-18T12:16:53.354ZS-EPMC60998973006141610.1073/pnas.1803599115