Abstract The reliable fabrication of high-sensitivity superconducting quantum interference devices (SQUIDs) with high critical transition temperature (high- T c ) is crucial for many practical applications such as weak magnetic sensing. In this work, we report the first realization of the YBa 2 Cu 3 O 7− δ (YBCO) radio frequency SQUIDs (rf SQUIDs) based on focused helium ion beam (FHIB) technique. A series of YBCO rf SQUIDs with high consistency were fabricated using a 30 keV FHIB with different helium ion (He + ) dose. The dose-dependent characteristics of the fabricated devices were systematically investigated at a temperature of 77 K. The experimental results verify that the variation in He + dose can effectively modulate the junction parameters and thereby the device noise performance. A non-monotonic white noise trend with increasing He + dose was observed, which could be primarily attributed to the transition of operational working regime of the fabricated rf SQUIDs. Based upon the dose optimization, a flux noise of 58 μ Φ 0 / H z 1 / 2 , corresponding to a field sensitivity of 185 f T / H z 1 / 2 , was achieved with our current device configuration. Approaches to further optimize the overall device performance are also discussed. Our work demonstrates FHIB-based high- T c SQUIDs with high junction parameter consistency a promising candidate for the implementation of multi-channel weak magnetic field detection systems and might hopefully serve as a platform for validating the theoretical models of high- T c SQUIDs.

Superconductor Science and TechnologyOct 1, 20260 citations

Multi-terminal multi-junction dc SQUID for nanoscale magnetometry

Alexander Y. Meltzer, Aviram Uri, Eli Zeldov

Abstract Miniaturization of superconducting quantum interference devices (SQUIDs) is of major importance for the development of sensitive scanning nanoscale magnetometry tools. The high sensitivity of nanoSQUIDs is restricted, however, to only particular periodic values of the applied magnetic field, making accurate measurements at intermediate values of the field impossible. We present a theoretical investigation of a multi-terminal, multi-junction SQUID (mSQUID) that lifts this limitation by providing electrical means for a continuous shift of the quantum interference pattern with respect to the applied field. Analysis of 4-terminal, 4-junction and 3-terminal, 3-junction mSQUIDs shows that operation at maximum sensitivity can be obtained at any value of the magnetic field by applying control current to the extra terminals. The model describes the variation and the shift of the interference pattern as a function of the control currents, junction asymmetries, and the mSQUID inductance. The mSQUID is also shown to provide a direct measurement of the current–phase relations of superconducting junctions. The derived model provides a quantitative description of the recently developed multi-terminal nanoSQUID-on-tip.

arXiv:1606.05682Superconductor Science and TechnologySep 26, 20168 citations