2015/09/24 by Ilya Belopolski, Su‐Yang Xu, Belopolski, Ilya +35
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #FOS: Physical sciences #Graphene research and applications #Magnetic properties of thin films #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #Topological Materials and Phenomena
paper · pdf · doi:10.48550/arxiv.1509.07465
openalex publication_date 2015/09/24 · openalex created_date 2019/07/30 · openalex updated_date 2026/07/28
The recent experimental discovery of a Weyl semimetal in TaAs provides the\nfirst observation of a Weyl fermion in nature and demonstrates a novel type of\nanomalous surface state band structure, consisting of Fermi arcs. So far, work\nhas focused on Weyl semimetals with strong spin-orbit coupling (SOC). However,\nWeyl semimetals with weak SOC may allow tunable spin-splitting for device\napplications and may exhibit a crossover to a spinless topological phase, such\nas a Dirac line semimetal in the case of spinless TaAs. NbP, isostructural to\nTaAs, may realize the first Weyl semimetal in the limit of weak SOC. Here we\nstudy the surface states of NbP by angle-resolved photoemission spectroscopy\n(ARPES) and we find that we \cannot show Fermi arcs based on our\nexperimental data alone. We present an \ab initio calculation of the\nsurface states of NbP and we find that the Weyl points are too close and the\nFermi level is too low to show Fermi arcs either by (1) directly measuring an\narc or (2) counting chiralities of edge modes on a closed path. Nonetheless,\nthe excellent agreement between our experimental data and numerical\ncalculations suggests that NbP is a Weyl semimetal, consistent with TaAs, and\nthat we observe trivial surface states which evolve continuously from the\ntopological Fermi arcs above the Fermi level. Based on these results, we\npropose a slightly different criterion for a Fermi arc which, unlike (1) and\n(2) above, does not require us to resolve Weyl points or the spin splitting of\nsurface states. We propose that raising the Fermi level by > 20 meV would\nmake it possible to observe a Fermi arc using this criterion in NbP. Our work\noffers insight into Weyl semimetals with weak spin-orbit coupling, as well as\nthe crossover from the spinful topological Weyl semimetal to the spinless\ntopological Dirac line semimetal.\n