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Dirac electron states formed at the heterointerface between a topological insulator and a conventional semiconductor


Topological insulators are a class of semiconductor exhibiting charge-gapped insulating behaviour in the bulk, but hosting a spin-polarized massless Dirac electron state at the surface1,2,3,4. The presence of a topologically protected helical edge channel has been verified for the vacuum-facing surface of several topological insulators by means of angle-resolved photoemission spectroscopy5,6,7 and scanning tunnelling microscopy8,9,10. By performing tunnelling spectroscopy on heterojunction devices composed of p-type topological insulator (Bi1xSbx)2Te3 and n-type conventional semiconductor InP, we report the observation of such states at the solid-state interface. Under an applied magnetic field, we observe a resonance in the tunnelling conductance through the heterojunction due to the formation of Landau levels of two-dimensional Dirac electrons at the interface. Moreover, resonant tunnelling spectroscopy reveals a systematic dependence of the Fermi velocity and Dirac point energy on the composition x. The successful formation of robust non-trivial edge channels at a solid-state interface is an essential step towards functional junctions based on topological insulators11,12,13.

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Figure 1: Tunnelling spectroscopy in a topological insulator/non-topological insulator p–n junction.
Figure 2: Landau-level formation observed in tunnelling spectra.
Figure 3: Angular dependence of Landau-level formation.
Figure 4: Composition dependence of Fermi velocity and energy of Dirac point in (Bi1xSbx)2Te3.


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This research was supported by the Japan Society for the Promotion of Science through the Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST Program) on ‘Quantum Science on Strong Correlation’ initiated by the Council for Science and Technology Policy and by JSPS Grant-in-Aid for Scientific Research(S) No. 24224009 and No. 24226002.

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Y.T. conceived the project. R.Y. and K.K. grew the thin films, made the devices and performed the tunnelling spectroscopy measurements. R.Y. analysed the data and wrote the manuscript with contributions from all authors. A.T., J.G.C., K.S.T., M.K. and Y.T. jointly discussed the results.

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Correspondence to R. Yoshimi.

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The authors declare no competing financial interests.

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Yoshimi, R., Tsukazaki, A., Kikutake, K. et al. Dirac electron states formed at the heterointerface between a topological insulator and a conventional semiconductor. Nature Mater 13, 253–257 (2014).

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