title: Electronic and optical properties of topological semimetal Cd3As2.
abstract: Using ab initio density functional theory the band structure and the dielectric function of a bct Cd3As2crystal are calculated. We find a Dirac semimetal with two Dirac nodes k±near the Γ point on the tetragonal axis. The bands near the Fermi level exhibit a linear behavior. The resulting Dirac cones are anisotropic and the electron-hole symmetry is destroyed along the tetragonal axis. Along this axis the symmetry-protected band linearity only exists in a small energy interval. The Dirac cones seemingly found by ARPES in a wider energy range are interpreted in terms of pseudo-linear bands. The behavior as 3D graphene-like material is traced back to As p orbital pointing to Cd vacancies, in directions which vary throughout the unit cell. Because of the Dirac nodes the dielectric functions (imaginary part) show a plateau for vanishing frequencies whose finite value is proportional to the Sommerfeld fine structure constant but varies with the light polarization. The consequences of the anisotropy of the Dirac cones are highlighted for the polarization dependence of the infrared optical conductivity.
authors.affiliation: ISMN, Consiglio Nazionale delle Ricerche, Via Salaria Km 29,300 00015 Monterotondo Stazione (Roma) - Italy.|Dipartimento di Fisica, Università di Roma 'Tor Vergata', Via della Ricerca Scientifica 1, I-00133, Rome, Italy.
authors.forename: Adriano
authors.initials: A
authors.lastname: Mosca Conte
authors.affiliation: Dipartimento di Fisica, Università di Roma 'Tor Vergata', Via della Ricerca Scientifica 1, I-00133, Rome, Italy.|I.N.F.N, - Sezione di Roma 'Tor Vergata', and CNR-ISM, Roma, Italy.
authors.forename: Olivia
authors.initials: O
authors.lastname: Pulci
authors.affiliation: IFTO, Friedrich-Schiller-Universität and ETSF, Max-Wien-Platz 1, 07743 Jena, Germany.
authors.forename: Friedhelm
authors.initials: F
authors.lastname: Bechstedt