Observation of three-dimensional massless Kane fermions in a zinc-blende crystal

• Published in: Nature physics Vol. 10; no. 3; pp. 233 - 238
• Main Authors: Orlita, M., Basko, D. M., Zholudev, M. S., Teppe, F., Knap, W., Gavrilenko, V. I., Mikhailov, N. N., Dvoretskii, S. A., Neugebauer, P., Faugeras, C., Barra, A-L., Martinez, G., Potemski, M.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.03.2014; Nature Publishing Group; Nature Publishing Group [2005-....]
• Subjects: 639/766/119/1000; 639/766/119/2792; 639/766/119/995; Atomic; Atomic and Molecular Clusters; Classical and Continuum Physics; Complex Systems; Condensed Matter Physics; Conductivity; Crystals; Dispersions; Electric properties; Fermions; Graphene; Magnetic fields; Materials science; Mathematical and Computational Physics; Molecular; Nanotechnology; Optical and Plasma Physics; Photons; Physics; Signatures; Solid state physics; Theoretical; Three dimensional; Zinc
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/nphys2857

Solid-state physics and quantum electrodynamics, with its ultrarelativistic (massless) particles, meet in the electronic properties of one-dimensional carbon nanotubes, two-dimensional graphene or topological-insulator surfaces. However, clear experimental evidence for electronic states with a conical dispersion relation in all three dimensions, conceivable for certain bulk materials, is still missing. Here, we study a zinc-blende crystal, HgCdTe, at the point of the semiconductor-to-semimetal topological transition. For this compound, we observe three-dimensional massless electrons, as certified from the dynamical conductivity increasing linearly with the photon frequency, with a velocity of about 10 6  m s −1 . Applying a magnetic field B results in a -dependence of dipole-active inter-Landau-level resonances and spin splitting of Landau levels also following a -dependence—well-established signatures of ultrarelativistic particles but until now not observed experimentally in any solid-state electronic system. Graphene and topological-insulator surfaces are well known for their two-dimensional conic electronic dispersion relation. Now three-dimensional hyperconic dispersion is shown for electrons in a HgCdTe crystal—once again bridging solid-state physics and quantum electrodynamics.