Abstract 23 September 2015 - morning

Epitaxial Al-InAs two-dimensional systems: a platform for topological superconductivity

Fabrizio Nichele, Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen

The realization of topological superconductivity and Majorana modes relies on the coupling between superconductors and semiconductors with strong spin-orbit interaction (SOI). So far, the most common approach for the realization of Majorana modes is based on semiconducting nanowires with strong SOI coupled to superconductors in the presence of a Zeeman field. This initial approach is supported by early experimental evidence [1].

Semiconductor nanowires are currently an attractive and successful building block for the study of Majorana modes. Their flexibility is nevertheless limited to two-terminal devices, and their extension to multi-terminal systems (such as those required for braiding operations) requires complex approaches [2].

I will present our recent experimental efforts aimed to overcome these difficulties and realize a flexible superconductor-semiconductor platform based on Al and the InAs two-dimensional electron gas (2DEG). Similarly to recent work on nanowires, the superconductor is deposited on the semiconductor directly in the growth chamber, allowing for an ideal Al-InAs epitaxial match [3,4]. Thanks to this approach, we largely solve the issues related to low-transparency interfaces in 2D systems.

In this talk I will present experimental results on gateable supercurrents in Al-InAs-Al Josephson junctions and tunneling spectroscopy of a hard superconducting gap in Al-InAs junctions. Our observations indicate great promise for the future realization of topological superconducting devices in these 2D systems.

[1] V. Mourik et al. Science 336, 1003–1007 (2012)

[2] J. Alicea et al. Nature Physics, 7, 412-417 (2011)

[3] P. Krostrup et al. Nature Materials 14, 400–406 (2015)

[4] W. Chang et al. Nature Nanotechnology 10, 232–236 (2015)



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