Abstract
Topological surface states of three-dimensional topological insulator nanoribbons and their distinct magnetoconductance properties are promising for topoelectronic applications and topological quantum computation. A crucial building block for nanoribbon-based circuits are three-terminal junctions. While the transport of topological surface states on a planar boundary is not directly affected by an in-plane magnetic field, the orbital effect cannot be neglected when the surface states are confined to the boundary of a nanoribbon geometry. Here, we report on the magnetotransport properties of such three-terminal junctions. We observe a dependence of the current on the in-plane magnetic field, with a distinct steering pattern of the surface state current towards a preferred output terminal for different magnetic field orientations. We demonstrate that this steering effect originates from the orbital effect, trapping the phase-coherent surface states in the different legs of the junction on opposite sides of the nanoribbon and breaking the left-right symmetry of the transmission across the junction. The reported magnetotransport properties demonstrate that an in-plane magnetic field is not only relevant but also very useful for the characterization and manipulation of transport in three-dimensional topological insulator nanoribbon-based junctions and circuits, acting as a topoelectric current switch.
Highlights
Topological surface states of three-dimensional topological insulator nanoribbons and their distinct magnetoconductance properties are promising for topoelectronic applications and topological quantum computation
The structures were prepared by employing selective-area molecular beam epitaxy (MBE) and the conductance was measured as a function of the angle between the magnetic field and the input lead
Sweeping the inplane field strength up to 0.5 T we observe a uniform decrease in the total current Itot, which we attribute to the weak antilocalization (WAL) effect present in the individual legs of the T-junction
Summary
Topological surface states of three-dimensional topological insulator nanoribbons and their distinct magnetoconductance properties are promising for topoelectronic applications and topological quantum computation. In addition to magnetotransport studies, first steps have been made to use this platform for hosting exotic quasiparticle states known as Majorana bound states (MBSs), by aligning a 3D TI nanowire with an external magnetic field and combining it with an s-wave superconductor for realizing topological superconductivity via the proximity effect[19,20,21,22,23] These states are of particular interest since they are promising candidates for the realization of fault-tolerant quantum computation[4,6,24,25,26,27]. In the single-channel limit, quantum transport simulations indicate that a complete pinch-off or near-perfect transparency of the topological surface state-based carrier transport can be realized to particular output legs for certain magnetic field orientations and strengths In this context, we have studied the low-temperature magnetotransport properties of Bi2Te3-based tri-junctions with three nanoribbon legs. To explain the observed features, we developed a qualitative tri-junction transmission model, based on our findings from semiclassical considerations and quantum transport simulations (with Kwant29) of topological surface states in 3D TI-based multiterminal junctions in the presence of an external magnetic field
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