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Properties of Grooved Dayem Bridge based YBa$_2$Cu$_3$O$_{7-delta}$ Superconducting Quantum Interference Devices and Magnetometers

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 نشر من قبل Edoardo Trabaldo
 تاريخ النشر 2020
  مجال البحث فيزياء
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The transport properties of a YBa$_2$Cu$_3$O$_{7-delta}$ superconducting quantum interference device (SQUID) based on grooved Dayem bridge weak links are studied as a function of temperature: at high temperatures ($60~$K$<T<T_mathrm{c}=89$~K) the weak links show properties similar to SNS junctions, while at temperatures below 60~K the weak links behave like short Dayem bridges. Using these devices, we have fabricated SQUID magnetometers with galvanically coupled in-plane pick-up loops: at $T=77$~K, magnetic field white noise levels as low as $63$~fT/$sqrt{mathrm{Hz}}$ have been achieved.



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We present noise measurements performed on a YBa$_2$Cu$_3$O$_{7-delta}$ nanoscale weak-link-based magnetometer consisting of a Superconducting QUantum Interference Device (SQUID) galvanically coupled to a $3.5 times 3.5~$mm$^2$ pick-up loop, reaching white flux noise levels and magnetic noise levels as low as $6~muPhi_0 / sqrt{mathrm{Hz}}$ and $100$~fT/$sqrt{mathrm{Hz}}$ at $T=77$~K, respectively. The low noise is achieved by introducing Grooved Dayem Bridges (GDBs), a new concept of weak-link. A fabrication technique has been developed for the realization of nanoscale grooved bridges, which substitutes standard Dayem bridge weak links. The introduction of these novel key blocks reduces the parasitic inductance of the weak links and increases the differential resistance of the SQUIDs. This greatly improves the device performance, thus resulting in a reduction of the white noise.
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