Progress in Superconductivity and Cryogenics (한국초전도ㆍ저온공학회논문지)

The Korean Society of Superconductivity and Cryogenics (한국초전도저온학회)
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Josephson effect of the superconducting van der Waals junction

  • Park, Sungyu (Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science) ;
  • Kwon, Chang Il (Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science) ;
  • Kim, Jun Sung (Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science)
  • Received : 2021.05.12
  • Accepted : 2021.05.22
  • Published : 2021.06.30
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Abstract

Heterostructures fabricated by various combinations of van der Waals (vdW) materials enable us to investigate disorder-free physical properties and realize novel functional devices. Superconducting vdW junctions have attracted a lot of attention because of its simple structure without a barrier layer. In superconducting vdW junction, without extra fabrication effort, a natural barrier can be formed, whose character is sensitive to distance and angle of lattice between two superconducting vdW materials. Using high-quality single crystals and the dry transfer technique, we fabricated the vertically stacked NbSe2/NbSe2 and FeSe/FeSe vdW junctions and investigated their Josephson junction properties. We found that in the FeSe junctions, Josephson coupling is extremely sensitive to the fabrication conditions, in contrast to the NbSe2 junctions. We attributed this distinct character of the FeSe junctions to surface instability and small Fermi surface of FeSe.

단결정의 덩어리 시료로부터 박리된 NbSe2와 FeSe 박막을 이용한 동종 초전도 vdW 접합을 만들고 저온전도측정을 통해 JJ 효과를 확인하였다. 각 물질의 초전도 틈을 측정하였으며 기존 결과와 잘 일치하는 것을 확인하였다. FeSe 접합의 경우 NbSe2 접합과 다르게 JJ가 구현되지 않는 경우가 다수 발생하는데 이는 NbSe2와 구분되는 FeSe의 특성때문으로 보이며 일관성있는 JJ 구현을 위해서 저온 접합이나 접합 각도 의존성을 통한 향후 연구가 필요하다. 그럼에도 불구하고, 본 연구 결과는 FeSe 2차원 결정을 이용해 JJ가 잘 구현될 수 있음을 실험적으로 보인 첫 사례로서 그 의의를 갖는다.

Keywords

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