Gate-induced decoupling of surface and bulk state properties in selectively-deposited Bi${}_2$Te${}_3$ nanoribbons

Abstract

Three-dimensional topological insulators (TIs) host helical Dirac surface states at the interface with a trivial insulator. In quasi-one-dimensional TI nanoribbon structures the wave function of surface charges extends phase-coherently along the perimeter of the nanoribbon, resulting in a quantization of transverse surface modes. Furthermore, as the inherent spin-momentum locking results in a Berry phase offset of $\pi$ of self-interfering charge carriers an energy gap within the surface state dispersion appears and all states become spin-degenerate. We investigate and compare the magnetic field dependent surface state dispersion in selectively deposited Bi${}_2$Te${}_3$ TI micro- and nanoribbon structures by analysing the gate voltage dependent magnetoconductance at cryogenic temperatures. While in wide microribbon devices the field effect mainly changes the amount of bulk charges close to the top surface we identify coherent transverse surface states along the perimeter of the nanoribbon devices responding to a change in top gate potential. We quantify the energetic spacing in between these quantized transverse subbands by using an electrostatic model that treats an initial difference in charge carrier densities on the top and bottom surface as well as remaining bulk charges. In the gate voltage dependent transconductance we find oscillations that change their relative phase by $\pi$ at half-integer values of the magnetic flux quantum applied coaxial to the nanoribbon, which is a signature for a magnetic flux dependent topological phase transition in narrow, selectively deposited TI nanoribbon devices.

20 pages, 5 figures

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Cited by in corpus (10)

• Superconducting diode effect due to magnetochiral anisotropy in topological insulator and Rashba nanowires
• Proximity-induced superconductivity in (Bi${}_{1-x}$Sb${}_x$)${}_2$Te${}_3$ topological-insulator nanowires
• Metallization and proximity superconductivity in topological insulator nanowires
• Robust and fragile Majorana bound states in proximitized topological insulator nanoribbons
• Low-energy modeling of three-dimensional topological insulator nanostructures
• Time-dependent driving and topological protection in the fractional Josephson effect
• Aharonov-Bohm and Altshuler-Aronov-Spivak oscillations in the quasi-ballistic regime in phase-pure GaAs/InAs core/shell nanowires
• Selective-Area Epitaxy of Bulk-Insulating (Bi${}_x$Sb${}_{1-x}$)${}_2$Te${}_3$ Films and Nanowires by Molecular Beam Epitaxy
• In-plane magnetic field driven conductance modulations in topological insulator kinks
• Electromagnetic response of the surface states of a topological insulator nanowire embedded within a resonator