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Investigating the intrinsic noise limit of Dayem bridge NanoSQUIDs.

Patel, T; Li, B*; Gallop, J C; Cox, D; Kirkby, K*; Romans, E*; Chen, J*; Nisbet, A*; Hao, L (2015) Investigating the intrinsic noise limit of Dayem bridge NanoSQUIDs. IEEE Trans. Appl. Supercond., 25 (3). 1602105

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NanoSQUIDs made from Nb thin films have been produced with nanometre loop sizes down to 200 nm, using weak-link junctions with dimensions less than 60 nm. These composite (W/Nb) single layer thin film devices, patterned by FIB milling, show extremely good low-noise performance ~170 n¿0 at temperatures between 5 K and 8.5 K and can operate in rather high magnetic fields (at least up to 1 T). The devices produced so far have a limited operating temperature range, typically only 1-2 K. We have the goal of achieving operation at 4.2 K, to be compatible with the best SQUID series array (SSA) preamplifier available. Using the SSA to readout the nanoSQUIDs provides us with a means of investigating the intrinsic noise of the former. In this paper we report improved white noise levels of these nanoSQUIDs, enabling potential detection of a single electronic spin flip in a 1Hz bandwidth. At low frequencies the noise performance is already limited by SSA preamplifier noise.

Item Type: Article
Keywords: NanoSQUIDs, noise measurements, Tc suppression
Subjects: Quantum Phenomena
Quantum Phenomena > Nanophysics
Identification number/DOI: 10.1109/TASC.2014.2364920
Last Modified: 02 Feb 2018 13:13
URI: http://eprintspublications.npl.co.uk/id/eprint/6475

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