title: Dirac and Weyl superconductors in three dimensions.
abstract: We introduce the concept of three-dimensional Dirac (Weyl) superconductors (SC), which have protected bulk fourfold (twofold) nodal points and surface Majorana arcs at zero energy. We provide a sufficient criterion for realizing them in centrosymmetric SCs with odd-parity pairing and mirror symmetry. Pairs of Dirac nodes appear in a mirror-invariant plane when the mirror winding number is nontrivial. Breaking mirror symmetry may gap Dirac nodes producing a topological SC. Each Dirac node evolves to a nodal ring when inversion-gauge symmetry is broken, whereas it splits into a pair of Weyl nodes when, and only when, time-reversal symmetry is broken.
authors.affiliation: Engineering Product Development, Singapore University of Technology and Design, Singapore 138682, Singapore.
authors.forename: Shengyuan A
authors.initials: SA
authors.lastname: Yang
authors.affiliation: Department of Physics, Beihang University, Beijing 100191, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Pan
authors.affiliation: Department of Physics, University of Texas at Dallas, Richardson, Texas 75080, USA and Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA and Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang