Subgap leakage and interface states in superconductor-insulator- superconductor tunnel junctions

Hyunsik Im, Yu A. Pashkin, Yongmin Kim, T. F. Li, Kyooho Jung, O. Astafiev, J. S. Tsai

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


We use tunneling spectroscopy in Al and Nb based superconductor-insulator- superconductor (SIS) junctions to demonstrate the existence of metallic quasiparticle states at the interface of a superconducting electrode and an oxide layer, introducing a new method to directly evaluate the interface quasiparticle areal density of states. Current-voltage (I-V) characteristics typically observed in metal-insulator-superconductor (MIS) junctions are observed in the subgap voltage region. The turn-on voltage of the MIS-type leakage is found to be determined by the superconducting electrode with a smaller gap energy (Δ), and its magnitude depends on the nature of the interface. Our experiment suggests that the interface plays a key role in contributing to the subgap leakage influencing the performance of superconducting circuits.

Original languageEnglish
Pages (from-to)S832-S833
JournalPhysica C: Superconductivity and its Applications
Issue numberSUPPL.1
Publication statusPublished - Dec 2010
Externally publishedYes


  • Angle deposition
  • Interface states
  • Subgap leakage
  • Tunneling spectroscopy


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