Are "Pinholes" the Cause of Excess Current in Superconducting Tunnel Junctions? A Study of Andreev Current in Highly Resistive Junctions
Journal article, 2011

In highly resistive superconducting tunnel junctions, excess subgap current is usually observed and is often attributed to microscopic pinholes in the tunnel barrier. We have studied the subgap current in superconductor-insulator-superconductor (SIS) and superconductor-insulator-normal-metal ( SIN) junctions. In Al/AlOx/Al junctions, we observed a decrease of 2 orders of magnitude in the current upon the transition from the SIS to the SIN regime, where it then matched theory. In Al/AlOx/Cu junctions, we also observed generic features of coherent diffusive Andreev transport in a junction with a homogenous barrier. We use the quasiclassical Keldysh-Green function theory to quantify single- and two-particle tunneling and find good agreement with experiment over 2 orders of magnitude in transparency. We argue that our observations rule out pinholes as the origin of the excess current.

gap structure

leakage

subgap conductivity

qubits

barrier transparency

contacts

nb/alox/nb

Author

Tine Greibe

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Markku Stenberg

Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics

Christopher Wilson

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Thilo Bauch

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Vitaly Shumeiko

Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics

Per Delsing

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Physical Review Letters

0031-9007 (ISSN) 1079-7114 (eISSN)

Vol. 106 9

Areas of Advance

Nanoscience and Nanotechnology (2010-2017)

Subject Categories

Physical Sciences

DOI

10.1103/PhysRevLett.106.097001

More information

Created

10/7/2017