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Topological Insulator based on semi-metallic alloy HgCdTe

Author(s): G. Tomaka, J. Grendysa, P. Śliż, D. Żak and E.M. Sheregii *

HgCdTe (MCT) alloy is a standard material with strong spin-orbital interplay which lifts the G8 band above the G6 oneThis is why a Dirac point (the G6 and G8 crossing causes a singularity in electron shape with linear dispersion and zero effective mass of fermions) is realized when the composition of MCT is various from HgTe to CdTe what makes the 3D topological Dirac semimetal HgCdTe as a natural analogue of graphene in 3D.
 This thesis is confirmed by way of the experimental consequences of the magneto-transport measurements over a extensive c program languageperiod of temperatures for nineteen layers of MCT (x ≈ zero.13 - zero.15) grown by means of MBE provided in our paper. That are samples of three series: series A - strained thin (about 100 nm thickness) layers on the GaAs/CdTe substrate; series AB – no strained thin layers on the ZnCdTe substrate and series B – thick (about 1000 nm thickness) layers on the ZnCdTe substrate. The results obtained for sample A9, namely, the Rxx(B) and Rxy(B) curves (see Fig. 1), show for different temperatures over wide range from 0.4 K to 50 K the well-defined quantized plateaus in Rxy with values h/(2e2) = 12.9 kΩ, accompanied by vanishing Rxx is observed at 0.4 K what explicitly indicate on the Integer Quantum Hall Effect (IQHE) and Shubnikov-de Haas (SdH) oscillations characteristic for 2D electron gas. The Rxx(B) and Rxy(B) curves are reproducible up to 20 K and above this temperature the Integer Quantum Hall Conductivity (IQHC) is observed up to 50 K. That can be defined by means of conductivity on topologically protected surface states (TPSS). An exquisite temperature stability of the SdH-oscillation period and amplitude is discovered inside the whole temperature c program language period of measurements as much as 50 okay for samples of series AB (Fig.2) and B also (see Fig.2). ). In the case of no strained layers (series AB and B) it is assumed that the TPSS contributes (and dominates) also to the conductance of the bulk samples.
Interpretation of received experimental effects could be based totally on the kp-theory of band structure  along with axial stresses (for samples of series A). The fan of Landau levels can be calculate using the Dirac equation with electron pace at the Fermi level vF= 106 m/s that is plenty larger than for other 3D Tis. As Topological Insulator (IT) HgCdTe have important advantageshigh cost of the Fermi pace – about similar to for graphene, which leads to an increase in the attractiveness of TI for future applications: as massless Weyl fermions.
  Fig. 1. The Rxx(B) and Rxy(B) curves for sample A9      Fig. 2.The Rxx(B) and Rxy(B) curves for sample AB9.


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