Abstract
AbstractQuasi‐1D nanowires of topological insulators are candidate structures in superconductor hybrid architectures for Majorana fermion based quantum computation schemes. Here, selectively grown Bi2Te3 topological insulator nanoribbons at cryogenic temperatures are investigated. The nanoribbons are defined in deep‐etched Si3N4/SiO2 nano‐trenches on a silicon (111) substrate followed by a selective area growth process via molecular beam epitaxy. The selective area growth is beneficial to the device quality, as no subsequent fabrication needs to be performed to shape the nanoribbons. In the diffusive transport regime of these unintentionally n‐doped Bi2Te3 topological insulator nanoribbons, electron trajectories are identified by analyzing angle dependent universal conductance fluctuation spectra. When the sample is tilted from a perpendicular to a parallel magnetic field orientation, these high frequent conductance modulations merge with low frequent Aharonov–Bohm type oscillations originating from the topologically protected surface states along the nanoribbon perimeter. For 500 nm wide Hall bars low frequent Shubnikov–de Haas oscillations are identified in a perpendicular magnetic field orientation. These reveal a topological, high‐mobility, 2D transport channel, partially decoupled from the bulk of the material.
Highlights
Three-dimensional topological insulators (3D TIs) are a new class of materials that have a bulk electronic gap but highly conductive surface states, which promise a gapless, Dirac-like dispersion relation and spin-momentum locking of charge carriers occupying these surface states [1, 2]. 3D TIs are no longer only interesting for basic research but this new material class has slowly matured as candidates for a wide spectrum of applications, including the possible use for topology based quantum computation schemes [3,4,5]
These arise e.g. in the vortex core of a type-II, s-wave superconductor at the interface towards a 3D TI [7]. Another possibility is to design quasi-1D nanowires of 3D TIs, proximitized by an s-wave superconductor, where two Majorana zero modes (MZMs) will arise at both ends of the nanowire [8, 9]
Nano Hall bars have been characterized in the variable temperature insert (VTI) cryostat
Summary
Three-dimensional topological insulators (3D TIs) are a new class of materials that have a bulk electronic gap but highly conductive surface states, which promise a gapless, Dirac-like dispersion relation and spin-momentum locking of charge carriers occupying these surface states [1, 2]. 3D TIs are no longer only interesting for basic research but this new material class has slowly matured as candidates for a wide spectrum of applications, including the possible use for topology based quantum computation schemes [3,4,5]. It is difficult to characterize the surface state properties of these materials electrically at low temperatures, as these are usually superimposed by bulk contributions [27] In such disordered nanoribbons with non-negligible bulk contributions G e2/h, the expected amplitude for the flux periodic oscillations in the nanoribbons cross section deviates from the simple periodic inclusion of one additional transport channel [23, 24]. Previous studies on MBE grown 3D TI nanoribbons have shown that magnetotransport measurements reveal favored, defect-based electron trajectories (’fingerprints’) in these TI nanodevices, that mainly originate from 2D planes, parallel to the sample surface [28] These are dependent on the individual arrangement of scattering centers in the bulk of the nanoscale device, and unique. The highly mobile two-dimensional sheet can be coined topological since a Berry phase offset of β ∼ π has been determined
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