Induced superconductivity in the quantum spin Hall edge
By S. Hart, H. Ren, T. Wagner, P. Leubner, M. Mühlbauer, C. Brüne, H. Buhmann, L. Molenkamp, A. Yacoby. Nature Physics, 2013
308 citations recorded by the source corpus.
Majorana fermions, which are their own antiparticles, are expected to exist in topological superconductors. A study using superconducting leads in contact with a quantum well reveals the presence of supercurrents along one-dimensional sample edges of a quantum spin Hall state. These edge supercurrents are topological. Topological insulators are a newly discovered phase of matter characterized by gapped bulk states surrounded by conducting boundary states1,2,3. Since their theoretical discovery, these materials have encouraged intense efforts to study their properties and capabilities. Among the most striking results of this activity are proposals to engineer a new variety of superconductor at the surfaces of topological insulators4,5. These topological superconductors would be capable of supporting localized Majorana fermions, particles whose braiding properties have been proposed as the basis of a fault-tolerant quantum computer6. Despite the clear theoretical motivation, a conclusive realization of topological superconductivity remains an outstanding experimental goal. Here we present measurements of superconductivity induced in two-dimensional HgTe/HgCdTe quantum wells, a material that becomes a quantum spin Hall insulator when the well width exceeds dC = 6.3 nm (ref. 7). In wells that are 7.5 nm wide, we find that supercurrents are confined to the one-dimensional sample edges as the bulk density is depleted. However, when the well width is decreased to 4.5 nm the edge supercurrents cannot be distinguished from those in the bulk. Our results provide evidence for supercurrents induced in the helical edges of the quantum spin Hall effect, establishing this system as a promising avenue towards topological superconductivity. In addition to directly confirming the existence of the topological edge channels, our results also provide a measurement of their widths, which range from 180 nm to 408 nm.
Subfields: Atomic and Molecular Physics, and Optics, Condensed Matter Physics, Materials Chemistry
View Paper: https://www.semanticscholar.org/paper/b96d8975d3fe67b57b0dbb9f2efd7b7cef4e9a94
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Citations in the corpus
- Topological superconductors: a review (2016, background): “The experimental situation for induced 1D superconductivity in the topological edge states of the 2D topological insulator HgTe is probably more promising; for example, it has been shown that proximity-induced superconductivity is clearly established in the 1D helical edge states [243] and the recen”