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

Abstract

http://arxiv.org/abs/1310.0969 The authors acknowledge helpful discussions with T. Brauner, R. Grill, M. Grynberg, A. A. Nersesyan, V. Novák, M. L. Sadowski and W. Zawadzki. The work has been supported by the ERC project MOMB, by EuroMagNET II under the EU Contract No. 228043, by the GDR-I project 'Semiconductor sources and detectors of THz frequencies' and by the Scientific Council of Montpellier II University. We also acknowledge the support received from the Ambassade de France en Russie for the French-Russian collaboration and exchange of PhD students.International audienceSolid-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 106 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

Two-Dimensional Massless Dirac Fermions in Antiferromagnetic AFe2As2 Chen1, Wang2, Song3 et al. 2017Phys. Rev. Lett.276220View full textAdd to dashboardCite

“…Therefore, massless fermions, which are characterized by band-degeneracy points and linear energy-momentum dispersions, are expected to exist in the AFM state of BaFe 2 As 2 [19,20,25,[28][29][30][31][32][33][34]. There are three types of massless fermions, including MDF, massless Kane fermions, and Weyl fermions [35][36][37][38][39][40][41][42]. Therein, massless Kane fermions and Weyl fermions are characterized by a heavy-hole valence band around the band-degeneracy point and pairs of degenerate nodes with opposite chirality, respectively [35][36][37][38][39], while in PCIS, the heavy-hole valence band is absent and the degenerate nodes have the same chirality [19,20,28,31], which preclude the association of the observed linear band dispersions by ARPES with massless Kane fermions and Weyl fermions.…”

“…Therefore, massless fermions, which are characterized by band-degeneracy points and linear energy-momentum dispersions, are expected to exist in the AFM state of BaFe 2 As 2 [19,20,25,[28][29][30][31][32][33][34]. There are three types of massless fermions, including MDF, massless Kane fermions, and Weyl fermions [35][36][37][38][39][40][41][42]. Therein, massless Kane fermions and Weyl fermions are characterized by a heavy-hole valence band around the…”

Optical spectroscopy study of the three-dimensional Dirac semimetalZrTe5

“…Significantly, several 35 , all of which are lack of inversion symmetries and were suggested to be candidates of Weyl semimetals. Furthermore, 3D massless electrons with huge Fermi velocity are certified by linear rising optical conductivity in the zinc-blende crystal Hg 1−x Cd x Te, with a proper doping concentration close to x=0.17 36 . What we observed here, however, is the first bulk evidence of a time reversal and space inversion symmetry protected 3D Dirac semimetal in the as-grown single crystal.…”

Infrared magneto-spectroscopy of two-dimensional and three-dimensional massless fermions: A comparison

“…The growth sequence started with ZnTe and CdTe buffer layers, followed by the MCT epilayer with gradually changing cadmium content x, see Ref. 15 for details. The 3D conical band develops at the point of semiconductor-to-semimetal transition (around x % 0:17 at low temperatures).…”

“…[14][15][16][17][18][19][20][21][22][23][24][25][26][27] The magnetic field significantly changes the character of the motion of charge carriers (cyclotron motion) and induces a considerable modulation of the density of electronic states due to the appearance of Landau levels (LLs). The Dirac-type systems, with conical bands and therefore strongly non-equidistant Landau levels, give rise to a fairly rich magneto-optical response, involving both intra-(cyclotron resonance) and inter-band excitations with a characteristic ffiffiffi B p dependence on the applied magnetic field.…”