MASSS-Weak-links in InAs nanowires

Project MASSS – Marie-Sklodowska Curie Action by Leandro Tosi

Weak-links in InAs nanowires

The ingredients that are necessary for the spin-splitting of Andreev States can be found in semiconducting nanowires. A general drawback of hybrid superconductor-semiconductor devices is the difficulty in getting good interfaces between the materials, degrading the induced superconductivity. A plattform that overcomes this difficulty  was obtained in Copenhagen by Peter Krogstrup and coworkers. In Peter Krogstrup's group they developed a procedure in which after growing an InAs nanowire, a layer of Al is epitaxilly deposited, fully covering the wire (References: P. Krogstrup et al., “Epitaxy of semiconductorsuperconductor nanowires”, Nat. Mater. 14, 400 (2015) and figure taken from W. Chang et al., “Hard gap in epitaxial semiconductor-superconductor nanowires”, Nature Nanotechnology 10, 232 (2015)) . 

  

Due to the atomically perfect interface, the electrons in the nanowire inherite similar superconducting properties as those in the Al. We obtained these wires from a collaboration with Peter's group and could fabricate our weak-links.

The weak-links are obtained by removing the Al in part of the wire as highlighted in the figure below. 

Marcelo Goffman in the Quantronics group performed DC transport experiments prior to the beginning of my MSC Action to get a first characterization of the conduction channels in the wire. The IV curves at different gate voltages applied with the close-by metallic electrode (in yellow in the figure) show particular features asociated with the presence of Multiple Andreev Reflections (MAR) (arising from the formation of Andreev states within the gap). From a fit of the MAR, the transmission of each channel can be extracted. As it shown in their work, the gate controls the transmision of the channels as well as the number of them. They found that it was possible to obtain few channels contributing to transport with high transmission. For more information on this see M. F. Goffman et al., “Conduction channels of an InAs-Al nanowire Josephson weak link”, New J. Phys. 19, 092002 (2017).  

 

Back to:

Continue with:

Back

Comments are closed.