Hard superconducting gap and diffusion-induced superconductors in Ge-Si nanowires

Joost Ridderbos, Matthias Brauns, Folkert K. de Vries, Jie Shen, Ang Li, Sebastian Kölling, Marcel A. Verheijen, Alexander Brinkman, Wilfred G. van der Wiel, Erik P.A.M. Bakkers, Floris A. Zwanenburg (Corresponding author)

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Abstract

We show a hard superconducting gap in a Ge-Si nanowire Josephson transistor up to in-plane magnetic fields of 250 mT, an important step toward creating and detecting Majorana zero modes in this system. A hard gap requires a highly homogeneous tunneling heterointerface between the superconducting contacts and the semiconducting nanowire. This is realized by annealing devices at 180 °C during which aluminum interdiffuses and replaces the germanium in a section of the nanowire. Next to Al, we find a superconductor with lower critical temperature (TC = 0.9 K) and a higher critical field (BC = 0.9-1.2 T). We can therefore selectively switch either superconductor to the normal state by tuning the temperature and the magnetic field and observe that the additional superconductor induces a proximity supercurrent in the semiconducting part of the nanowire even when the Al is in the normal state. In another device where the diffusion of Al rendered the nanowire completely metallic, a superconductor with a much higher critical temperature (TC = 2.9 K) and critical field (BC = 3.4 T) is found. The small size of these diffusion-induced superconductors inside nanowires may be of special interest for applications requiring high magnetic fields in arbitrary direction.

Original languageEnglish
Pages (from-to)122-130
Number of pages9
JournalNano Letters
Volume20
Issue number1
DOIs
Publication statusPublished - 8 Jan 2020

Fingerprint

Superconducting materials
Nanowires
nanowires
Magnetic fields
critical temperature
magnetic fields
Germanium
Aluminum
Temperature
proximity
germanium
Transistors
transistors
switches
Tuning
tuning
Switches
Annealing
aluminum
annealing

Keywords

  • Ge−Si nanowire
  • hard superconducting gap
  • Josephson junction
  • Majorana quasiparticle
  • Superconductor−semiconductor hybrid device
  • topological superconductivity

Cite this

Ridderbos, J., Brauns, M., de Vries, F. K., Shen, J., Li, A., Kölling, S., ... Zwanenburg, F. A. (2020). Hard superconducting gap and diffusion-induced superconductors in Ge-Si nanowires. Nano Letters, 20(1), 122-130. https://doi.org/10.1021/acs.nanolett.9b03438
Ridderbos, Joost ; Brauns, Matthias ; de Vries, Folkert K. ; Shen, Jie ; Li, Ang ; Kölling, Sebastian ; Verheijen, Marcel A. ; Brinkman, Alexander ; van der Wiel, Wilfred G. ; Bakkers, Erik P.A.M. ; Zwanenburg, Floris A. / Hard superconducting gap and diffusion-induced superconductors in Ge-Si nanowires. In: Nano Letters. 2020 ; Vol. 20, No. 1. pp. 122-130.
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abstract = "We show a hard superconducting gap in a Ge-Si nanowire Josephson transistor up to in-plane magnetic fields of 250 mT, an important step toward creating and detecting Majorana zero modes in this system. A hard gap requires a highly homogeneous tunneling heterointerface between the superconducting contacts and the semiconducting nanowire. This is realized by annealing devices at 180 °C during which aluminum interdiffuses and replaces the germanium in a section of the nanowire. Next to Al, we find a superconductor with lower critical temperature (TC = 0.9 K) and a higher critical field (BC = 0.9-1.2 T). We can therefore selectively switch either superconductor to the normal state by tuning the temperature and the magnetic field and observe that the additional superconductor induces a proximity supercurrent in the semiconducting part of the nanowire even when the Al is in the normal state. In another device where the diffusion of Al rendered the nanowire completely metallic, a superconductor with a much higher critical temperature (TC = 2.9 K) and critical field (BC = 3.4 T) is found. The small size of these diffusion-induced superconductors inside nanowires may be of special interest for applications requiring high magnetic fields in arbitrary direction.",
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Ridderbos, J, Brauns, M, de Vries, FK, Shen, J, Li, A, Kölling, S, Verheijen, MA, Brinkman, A, van der Wiel, WG, Bakkers, EPAM & Zwanenburg, FA 2020, 'Hard superconducting gap and diffusion-induced superconductors in Ge-Si nanowires', Nano Letters, vol. 20, no. 1, pp. 122-130. https://doi.org/10.1021/acs.nanolett.9b03438

Hard superconducting gap and diffusion-induced superconductors in Ge-Si nanowires. / Ridderbos, Joost; Brauns, Matthias; de Vries, Folkert K.; Shen, Jie; Li, Ang; Kölling, Sebastian; Verheijen, Marcel A.; Brinkman, Alexander; van der Wiel, Wilfred G.; Bakkers, Erik P.A.M.; Zwanenburg, Floris A. (Corresponding author).

In: Nano Letters, Vol. 20, No. 1, 08.01.2020, p. 122-130.

Research output: Contribution to journalArticleAcademicpeer-review

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T1 - Hard superconducting gap and diffusion-induced superconductors in Ge-Si nanowires

AU - Ridderbos, Joost

AU - Brauns, Matthias

AU - de Vries, Folkert K.

AU - Shen, Jie

AU - Li, Ang

AU - Kölling, Sebastian

AU - Verheijen, Marcel A.

AU - Brinkman, Alexander

AU - van der Wiel, Wilfred G.

AU - Bakkers, Erik P.A.M.

AU - Zwanenburg, Floris A.

PY - 2020/1/8

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N2 - We show a hard superconducting gap in a Ge-Si nanowire Josephson transistor up to in-plane magnetic fields of 250 mT, an important step toward creating and detecting Majorana zero modes in this system. A hard gap requires a highly homogeneous tunneling heterointerface between the superconducting contacts and the semiconducting nanowire. This is realized by annealing devices at 180 °C during which aluminum interdiffuses and replaces the germanium in a section of the nanowire. Next to Al, we find a superconductor with lower critical temperature (TC = 0.9 K) and a higher critical field (BC = 0.9-1.2 T). We can therefore selectively switch either superconductor to the normal state by tuning the temperature and the magnetic field and observe that the additional superconductor induces a proximity supercurrent in the semiconducting part of the nanowire even when the Al is in the normal state. In another device where the diffusion of Al rendered the nanowire completely metallic, a superconductor with a much higher critical temperature (TC = 2.9 K) and critical field (BC = 3.4 T) is found. The small size of these diffusion-induced superconductors inside nanowires may be of special interest for applications requiring high magnetic fields in arbitrary direction.

AB - We show a hard superconducting gap in a Ge-Si nanowire Josephson transistor up to in-plane magnetic fields of 250 mT, an important step toward creating and detecting Majorana zero modes in this system. A hard gap requires a highly homogeneous tunneling heterointerface between the superconducting contacts and the semiconducting nanowire. This is realized by annealing devices at 180 °C during which aluminum interdiffuses and replaces the germanium in a section of the nanowire. Next to Al, we find a superconductor with lower critical temperature (TC = 0.9 K) and a higher critical field (BC = 0.9-1.2 T). We can therefore selectively switch either superconductor to the normal state by tuning the temperature and the magnetic field and observe that the additional superconductor induces a proximity supercurrent in the semiconducting part of the nanowire even when the Al is in the normal state. In another device where the diffusion of Al rendered the nanowire completely metallic, a superconductor with a much higher critical temperature (TC = 2.9 K) and critical field (BC = 3.4 T) is found. The small size of these diffusion-induced superconductors inside nanowires may be of special interest for applications requiring high magnetic fields in arbitrary direction.

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KW - Majorana quasiparticle

KW - Superconductor−semiconductor hybrid device

KW - topological superconductivity

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