Gate-tuned normal and superconducting transport at the surface of a topological insulator

Abstract

Three-dimensional topological insulators are characterized by the presence of a bandgap in their bulk and gapless Dirac fermions at their surfaces. New physical phenomena originating from the presence of the Dirac fermions are predicted to occur, and to be experimentally accessible via transport measurements in suitably designed electronic devices. Here we study transport through superconducting junctions fabricated on thin Bi2Se3 single crystals, equipped with a gate electrode. In the presence of perpendicular magnetic field B, sweeping the gate voltage enables us to observe the filling of the Dirac fermion Landau levels, whose character evolves continuously from electron- to hole-like. When B=0, a supercurrent appears, whose magnitude can be gate tuned, and is minimum at the charge neutrality point determined from the Landau level filling. Our results demonstrate how gated nano-electronic devices give control over normal and superconducting transport of Dirac fermions at an individual surface of a three-dimensional topological insulators.

Quantum oscillations of the topological surface states in low carrier concentration crystals of Bi2−xSbxTe3Pan1, Никитин2, Wu3 et al. 2016Solid State Communications7100View full textAdd to dashboardCite

“…Clearly, these values differ from the value π expected for topological surface states. A Berry phase extracted in this way that deviates from π has been reported frequently in other SdH studies on the 3D TI family (Bi,Sb) 2 (Te,Se) 3 [11,12,26,33,27]. However, obtaining n x by linear extrapolation is not justified in all cases.…”

Nearly flat Andreev bound states in superconductor-topological insulator hybrid structures

“…[19][20][21][22][23]. Gate tunable supercurrent has been observed and argued to be due to the TI surface state [19].…”

Topological Insulator Materials

“…103,104,108,170,171,184,[229][230][231] Since it is important to clarify this confusion, let us discuss this issue in some detail. In solids, the resistivity tensor is an inverse of the conductivity tensor, and in the isotropic case their relation is …”

“…The former can be done by looking at the sample-size dependence of the conductance, 108,[140][141][142] and the latter may be accomplished by elucidating the Berry phase in the quantum oscillations from the surface state. 103,104,108,[170][171][172][173] (Detailed discussions on the identification of the Berry phase will be given in Sect. 8.3.)…”