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4π-periodic Andreev bound states in a Dirac semimetal.

Authors :: Li C
de Boer JC
de Ronde B
Ramankutty SV
van Heumen E
Huang Y
de Visser A
Golubov AA
Golden MS
Brinkman A
Source :: Nature materials [Nat Mater] 2018 Oct; Vol. 17 (10), pp. 875-880. Date of Electronic Publication: 2018 Sep 17.
Publication Year :: 2018
Abstract: Although signatures of superconductivity in Dirac semimetals have been reported, for instance by applying pressure or using point contacts, our understanding of the topological aspects of Dirac semimetal superconductivity is still developing. Here, we utilize nanoscale phase-sensitive junction technology to induce superconductivity in the Dirac semimetal Bi <subscript>1-x</subscript> Sb <subscript>x</subscript> . Our radiofrequency irradiation experiments then reveal a significant contribution of 4π-periodic Andreev bound states to the supercurrent in Nb-Bi <subscript>0.97</subscript> Sb <subscript>0.03</subscript> -Nb Josephson junctions. The conditions for a substantial 4π contribution to the supercurrent are favourable because of the Dirac cone's very broad transmission resonances and a measurement frequency faster than the quasiparticle poisoning rate. In addition, we show that a magnetic field applied in the plane of the junction allows tuning of the Josephson junctions from 0 to π regimes. Our results open the technologically appealing avenue of employing the topological bulk properties of Dirac semimetals for topological superconductivity research and topological quantum computer development.