Tuning the inductance of Josephson junction arrays without SQUIDs

• Published in: Applied physics letters Vol. 123; no. 18
• Main Authors: Kuzmin, R., Mehta, N., Grabon, N., Manucharyan, V. E.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 30-10-2023
• Subjects: Applied physics; Arrays; Bends; Inductance; Inductors; Interference; Josephson junctions; Magnetic fields; Superconducting quantum interference devices; Transmission lines; Tunnel junctions
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/5.0171047

It is customary to use arrays of superconducting quantum interference devices (SQUIDs) for implementing magnetic field-tunable inductors. Here, we demonstrate an equivalent tunability in a (SQUID-free) array of single Al/AlOx/Al Josephson tunnel junctions. With the proper choice of junction geometry, a perpendicularly applied magnetic field bends along the plane of the superconductor and focuses into the tunnel barrier region due to a demagnetization effect. Consequently, the Josephson inductance can be efficiently modulated by the Fraunhofer-type supercurrent interference. The elimination of SQUIDs not only simplifies the device design and fabrication but also facilitates a denser packing of junctions, and, hence, a higher inductance per unit length. As an example, we demonstrate a transmission line, the characteristic impedance of which is field-tuned in the range of
4
–
8

k
Ω, centered around the important value of the resistance quantum
h
/
(
2
e
)
2
≈
6.5

k
Ω.