Topological insulators hold promise as a platform for unique quantum phenomena. However, realizing these phenomena experimentally requires sophisticated devices. In a Technical Review in Nature Reviews Physics, ML4Q spokesperson Yoichi Ando and ML4Q associated member Oliver Breunig discuss four topics of particular interest for topological insulator devices: topological superconductivity, quantum anomalous Hall insulators as a platform for exotic phenomena, spintronic functionalities and topological mesoscopic physics. They  also discuss the status and technical challenges in fabricating TI devices to address new physics.

Publication: Breunig, O., Ando, Y. Opportunities in topological insulator devices. Nat Rev Phys (2021).
https://doi.org/10.1038/s42254-021-00402-6

Images of topological insulator nanowire devices | For detailed description have a look at the review (image courtesy of Felix Münning and Dingxun Fan).

Specifically, the authors present the following key points:

• Interesting quantum phenomena deriving from the peculiar properties of topological insulators (TIs) can be observed in TI devices. Fabrication of such devices should take into account the special challenges these materials pose for fabrication.
• In proximity to a conventional superconductor, TIs can realize a topological superconducting state hosting Majorana zero modes, representing the main ingredient for topological quantum computing, in which TIs can potentially have an advantage over semiconductor platforms.
• By magnetically doping a TI, the quantum anomalous Hall effect can be observed if the Fermi level is tuned into the magnetic exchange gap and chiral edge states arise that are expected to turn into chiral Majorana edge states if superconductivity is induced by the proximity effect.
• The spin- momentum- locked surface states of a TI are potentially useful for spintronic applications due to their current- induced spin polarization that interacts with ferromagnetic electrodes.
• Quantum confinement in mesoscopic- sized TI nanowires leads to the formation of a peculiar Dirac subband structure, which can be modified by magnetic and electricfields to open extended topological phases within which Majorana zero modes are expected if proximitized by a superconductor. [Read more about that in this publication]
• Fabricating devices based on TIs and interfacing them with ferromagnets or superconductors requires well- tuned processes in order to preserve and control the surface state properties.

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