title: Dirac electron states formed at the  heterointerface between a topological  insulator and a conventional semiconductor.
abstract: 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 surface. 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 spectroscopy and scanning tunnelling microscopy. By performing tunnelling spectroscopy on heterojunction devices composed of p-type topological insulator (Bi1−xSbx)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 insulators.
authors.forename: R
authors.initials: R
authors.lastname: Yoshimi
authors.forename: A
authors.initials: A
authors.lastname: Tsukazaki
authors.forename: K
authors.initials: K
authors.lastname: Kikutake
authors.forename: J G
authors.initials: JG
authors.lastname: Checkelsky
authors.forename: K S
authors.initials: KS
authors.lastname: Takahashi
authors.forename: M
authors.initials: M
authors.lastname: Kawasaki
authors.forename: Y
authors.initials: Y
authors.lastname: Tokura