Microscopic mechanism of excess subgap transport in the present junctions

Determine whether barrier states, Nb/AlOₓ interface states, or another microscopic mechanism explain the non-ideal subgap transport observed in the present Nb-Al-AlOₓ-TiW tunnel junctions.

Background

The fitted Dynes parameters provide an effective description of strong subgap broadening, but earlier work on related Al-AlOₓ-Nb junctions attributed unexplained excess subgap current to possible barrier or interface states only tentatively. The authors explicitly state that the mechanism proposed for those earlier junctions cannot be assigned to the present device using the available measurements.

References

However, the microscopic mechanism proposed for those junctions cannot be assigned to the present device based on the available measurements.

— Electronic cooling of a TiW alloy normal-metal island using Nb-based superconducting tunnel junctions  (2608.24455 - Hätinen et al., 25 Aug 2026) in Main text, paragraph discussing non-ideal transport in Nb-based AlOₓ tunnel junctions