TY - JOUR
T1 - Are Pinholes the Cause of Excess Current in Superconducting Tunnel Junctions?
T2 - A Study of Andreev Current in Highly Resistive Junctions
AU - Greibe, Tine
AU - Stenberg, Markku P.V.
AU - Wilson, C.M.
AU - Bauch, Thilo
AU - Shumeiko, Vitaly S.
AU - Delsing, Per
PY - 2011
Y1 - 2011
N2 - 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.
AB - 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.
U2 - 10.1103/PhysRevLett.106.097001
DO - 10.1103/PhysRevLett.106.097001
M3 - Journal article
C2 - 21405645
SN - 0031-9007
VL - 106
JO - Physical Review Letters
JF - Physical Review Letters
IS - 9
M1 - 097001
ER -