Improved coupling of nanowire-based high-T-c SQUID magnetometers-simulations and experiments
Journal article, 2017

Superconducting quantum interference devices (SQUIDs) based on high critical-temperature superconducting nanowire junctions were designed, fabricated, and characterized in terms of their potential as magnetometers for magnetoencephalography (MEG). In these devices, the high kinetic inductance of junctions and the thin film thickness (50 nm) pose special challenges in optimizing the field coupling. The high kinetic inductance also brings difficulties in reaching a low SQUID noise. To explore the technique for achieving a high field sensitivity, single-layer devices with a directly connected pickup loop and flip-chip devices with an inductively coupled flux transformer using a two-level coupling approach were fabricated and tested. Two-level coupling is an approach designed for flip-chip nanowire-based SQUIDs, in which a washer type SQUID pickup loop is introduced as an intermediate coupling level between the SQUID loop and the flux transformer input coil. The inductances and effective areas of all these devices were simulated. We found that at T = 77 K, flip-chip devices with the two-level coupling approach (coupling coefficient of 0.37) provided the best effective area of 0.46 mm(2) among all the tested devices. With a flux noise level of 55 mu Phi(0) Hz-1/2, the field sensitivity level was 240 fTHz-1/2. This sensitivity is not yet adequate for MEG applications but it is the best level ever reached for nanowire-based high-Tc SQUID magnetometers.

high-T-c SQUID

coupling approach

flux transformer

nanowire

magnetometer

Author

Minshu Xie

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

Maxim Chukharkin Leonidovich

Chalmers, Microtechnology and Nanoscience (MC2)

Silvia Ruffieux

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

Justin Schneiderman

Alexei Kalaboukhov

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

Marco Arzeo

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

Thilo Bauch

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

Floriana Lombardi

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

Dag Winkler

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

Superconductor Science and Technology

0953-2048 (ISSN) 1361-6668 (eISSN)

Vol. 30 11

Areas of Advance

Nanoscience and Nanotechnology (2010-2017)

Subject Categories

Condensed Matter Physics

DOI

10.1088/1361-6668/aa8e14

More information

Created

11/8/2017