title: Criteria for Directly Detecting Topological Fermi Arcs in Weyl Semimetals.
abstract: The recent discovery of the first Weyl semimetal in TaAs provides the first observation of a Weyl fermion in nature and demonstrates a novel type of anomalous surface state, the Fermi arc. Like topological insulators, the bulk topological invariants of a Weyl semimetal are uniquely fixed by the surface states of a bulk sample. Here we present a set of distinct conditions, accessible by angle-resolved photoemission spectroscopy (ARPES), each of which demonstrates topological Fermi arcs in a surface state band structure, with minimal reliance on calculation. We apply these results to TaAs and NbP. For the first time, we rigorously demonstrate a nonzero Chern number in TaAs by counting chiral edge modes on a closed loop. We further show that it is unreasonable to directly observe Fermi arcs in NbP by ARPES within available experimental resolution and spectral linewidth. Our results are general and apply to any new material to demonstrate a Weyl semimetal.
authors.affiliation: Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Ilya
authors.initials: I
authors.lastname: Belopolski
authors.affiliation: Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Su-Yang
authors.initials: SY
authors.lastname: Xu
authors.affiliation: Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Sanchez
authors.affiliation: Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore.|Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore.
authors.forename: Guoqing
authors.initials: G
authors.lastname: Chang
authors.affiliation: International Center for Quantum Materials, Peking University, Beijing 100871, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Guo
authors.affiliation: Condensed Matter and Magnet Science Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.|Department of Physics, University of Central Florida, Orlando, Florida 32816, USA.
authors.forename: Madhab
authors.initials: M
authors.lastname: Neupane
authors.affiliation: Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Hao
authors.initials: H
authors.lastname: Zheng
authors.affiliation: Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore.|Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore.
authors.forename: Chi-Cheng
authors.initials: CC
authors.lastname: Lee
authors.affiliation: Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore.|Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore.
authors.forename: Shin-Ming
authors.initials: SM
authors.lastname: Huang
authors.affiliation: Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Guang
authors.initials: G
authors.lastname: Bian
authors.affiliation: Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Nasser
authors.initials: N
authors.lastname: Alidoust
authors.affiliation: Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.|Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: Tay-Rong
authors.initials: TR
authors.lastname: Chang
authors.affiliation: Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore.|Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore.|Department of Physics, Northeastern University, Boston, Massachusetts 02115, USA.
authors.forename: BaoKai
authors.initials: B
authors.lastname: Wang
authors.affiliation: International Center for Quantum Materials, Peking University, Beijing 100871, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Physics, Northeastern University, Boston, Massachusetts 02115, USA.
authors.forename: Arun
authors.initials: A
authors.lastname: Bansil
authors.affiliation: Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan.|Institute of Physics, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Horng-Tay
authors.initials: HT
authors.lastname: Jeng
authors.affiliation: Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore.|Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore.
authors.forename: Hsin
authors.initials: H
authors.lastname: Lin
authors.affiliation: International Center for Quantum Materials, Peking University, Beijing 100871, China.
authors.forename: Shuang
authors.initials: S
authors.lastname: Jia
authors.affiliation: Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: M Zahid
authors.initials: MZ
authors.lastname: Hasan