Are "Pinholes" the Cause of Excess Current in Superconducting Tunnel Junctions? A Study of Andreev Current in Highly Resistive Junctions
Artikel i vetenskaplig tidskrift, 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

Författare

Tine Greibe

Chalmers, Mikroteknologi och nanovetenskap (MC2), Kvantkomponentfysik

Markku Stenberg

Chalmers, Mikroteknologi och nanovetenskap (MC2), Tillämpad kvantfysik

Christopher Wilson

Chalmers, Mikroteknologi och nanovetenskap (MC2), Kvantkomponentfysik

Thilo Bauch

Chalmers, Mikroteknologi och nanovetenskap (MC2), Kvantkomponentfysik

Vitaly Shumeiko

Chalmers, Mikroteknologi och nanovetenskap (MC2), Tillämpad kvantfysik

Per Delsing

Chalmers, Mikroteknologi och nanovetenskap (MC2), Kvantkomponentfysik

Physical Review Letters

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

Vol. 106 9

Styrkeområden

Nanovetenskap och nanoteknik

Ämneskategorier

Fysik

DOI

10.1103/PhysRevLett.106.097001