Quantum confinement of the Dirac surface states in topological-insulator nanowires

Abstract

The non-trivial topology of the three-dimensional (3D) topological insulator (TI) dictates the appearance of gapless Dirac surface states. Intriguingly, when a 3D TI is made into a nanowire, a gap opens at the Dirac point due to the quantum confinement, leading to a peculiar Dirac sub-band structure. This gap is useful for, e.g., future Majorana qubits based on TIs. Furthermore, these Dirac sub-bands can be manipulated by a magnetic flux and are an ideal platform for generating stable Majorana zero modes (MZMs), which play a key role in topological quantum computing. However, direct evidence for the Dirac sub-bands in TI nanowires has not been reported so far. Here we show that by growing very thin ($\sim$40-nm diameter) nanowires of the bulk-insulating topological insulator (Bi${}_{1-x}$Sb${}_x$)${}_2$Te${}_3$ and by tuning its chemical potential across the Dirac point with gating, one can unambiguously identify the Dirac sub-band structure. Specifically, the resistance measured on gate-tunable four-terminal devices was found to present non-equidistant peaks as a function of the gate voltage, which we theoretically show to be the unique signature of the quantum-confined Dirac surface states. These TI nanowires open the way to address the topological mesoscopic physics, and eventually the Majorana physics when proximitised by an $s$-wave superconductor.

7 pages main text, 6 pages supplemental material

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• Observation of Dirac Holes and Electrons in a Topological Insulator
• Gate capacitance of back-gated nanowire field-effect transistors
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• Quantum confinement of the Dirac surface states in topological-insulator nanowires
• Bulk-Free Topological Insulator Bi2Se3 nanoribbons with Magnetotransport Signatures of Dirac Surface States
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Cited by in corpus (19)

• Opportunities in topological insulator devices
• Superconducting diode effect due to magnetochiral anisotropy in topological insulator and Rashba nanowires
• Giant magnetochiral anisotropy from quantum confined surface states of topological insulator nanowires
• Quantum confinement of the Dirac surface states in topological-insulator nanowires
• Spin-resolved thermal signatures of Majorana-Kondo interplay in double quantum dots
• Majorana bound states in topological insulators without a vortex
• Proximity-induced superconductivity in (Bi${}_{1-x}$Sb${}_x$)${}_2$Te${}_3$ topological-insulator nanowires
• Top-down fabrication of bulk-insulating topological insulator nanowires for quantum devices
• Metallization and proximity superconductivity in topological insulator nanowires
• Robust and fragile Majorana bound states in proximitized topological insulator nanoribbons
• Finite-size effects in cylindrical topological insulators
• Characterizing the chemical potential disorder in the topological insulator (Bi${}_{1-x}$Sb${}_x$)${}_2$Te${}_3$ thin films
• Electrostatic effects of the MnBi2Te4-superconductor hetero-structures in chiral Majorana search
• Fabry-Pérot interferometry with gate-tunable 3D topological insulator nanowires
• Anisotropic transport properties in prismatic topological insulator nanowires
• Aharanov-Bohm oscillations and perfectly transmitted mode in amorphous topological insulator nanowires
• Electronic confinement of surface states in a topological insulator nanowire
• Electromagnetic response of the surface states of a topological insulator nanowire embedded within a resonator
• Equatorial magnetoplasma waves