Three-dimensional Dirac cone carrier dynamics inNa3BiandCd3As2

2016/05/31 by Gregory S. Jenkins, G. S. Jenkins, Christopher Lane +21 · 1 citation
Materials Science · Physics and Astronomy · #2D Materials and Applications #Atomic physics #Condensed matter physics #Dirac (video compression format) #Excited state #Fermi level #Graphene research and applications #Phonon #Physics #Quantum mechanics #Topological Materials and Phenomena #cond-mat.str-el

paper · pdf · doi:10.1103/physrevb.94.085121

published as Physical Review B 94, 085121 (2016) · 15 pages, 6 figures, 3 tables

openalex created_date 2016/06/24 · arxiv created 2016/07/05 · openalex publication_date 2016/08/12 · arxiv updated 2016/08/17 · openalex updated_date 2026/08/06

Abstract

Optical measurements and band structure calculations are reported on three-dimensional Dirac materials. The electronic properties associated with the Dirac cone are identified in the reflectivity spectra of Cd₃As₂ and Na₃Bi single crystals. In Na₃Bi, the plasma edge is found to be strongly temperature dependent due to thermally excited free carriers in the Dirac cone. The thermal behavior provides an estimate of the Fermi level E_F=25 meV and the z-axis Fermi velocity v_z=0.3 eV \AA associated with the heavy bismuth Dirac band. At high energies above the \mathrm\ensuremathΓ-point Lifshitz gap energy, a frequency- and temperature-independent \ensuremathε₂ indicative of Dirac cone interband transitions translates into an ab-plane Fermi velocity of 3 eV \AA. The observed number of IR phonons rules out the P6₃/mmc space-group symmetry but is consistent with the P3c1 candidate symmetry. A plasmaron excitation is discovered near the plasmon energy that persists over a broad range of temperature. The optical signature of the large joint density of states arising from saddle points at \mathrm\ensuremathΓ is strongly suppressed in Na₃Bi, consistent with band structure calculations that show the dipole transition-matrix elements to be weak due to the very small s-orbital character of the Dirac bands. In Cd₃As₂, a distinctive peak in reflectivity due to the logarithmic divergence in \ensuremathε₁ expected at the onset of Dirac cone interband transitions is identified. The center frequency of the peak shifts with temperature quantitatively consistent with a linear dispersion and a carrier density of n=1.3\ifmmode×\else\texttimes\fi10¹⁷\phantom\rule4.pt0excm^\ensuremath-3. The peak width gives a measure of the Fermi-velocity anisotropy of 10%, indicating a nearly spherical Fermi surface. The line shape gives an upper bound estimate of 7 meV for the potential fluctuation energy scale.

Citations

• Signatures of Majorana fermions in hybrid superconductor-semiconductor nanowire devices
• Charge Carrier Interaction with a Purely Electronic Collective Mode: Plasmarons and the Infrared Response of Elemental Bismuth
• Topological insulators and superconductors
• Landau quantization and quasiparticle interference in the three-dimensional Dirac semimetal Cd3As2
• Observation of a three-dimensional topological Dirac semimetal phase in high-mobility Cd3As2
• A stable three-dimensional topological Dirac semimetal Cd3As2
• Observation of Majorana Fermions in Ferromagnetic Atomic Chains on a Superconductor
• Topological Insulators
• Discovery of a Weyl fermion semimetal and topological Fermi arcs
• Weyl Semimetal Phase in Noncentrosymmetric Transition-Metal Monophosphides
• Interband optical conductivity of the [001]-oriented Dirac semimetalCd3As2

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• Type-II Weyl cone transitions in driven semimetals