High--$T_c$ RF SQUIDs with Large Inductance of Quantization Loop

TL;DR

This paper reports the experimental observation of quantum interference in high-temperature superconductor RF SQUIDs with large inductance loops, demonstrating their potential for sensitive magnetic measurements at 77 K.

Contribution

It presents the first observation of steady quantum interference in RF SQUIDs with inductance as high as 6.6 nH, produced by a thick-film HTS technique, and introduces a new method to evaluate their sensitivity.

Findings

Quantum interference observed in large inductance RF SQUIDs.

Successful fabrication of high-$T_c$ SQUIDs with inductance up to 6.6 nH.

Proposed a new method to assess SQUID sensitivity.

Abstract

Experimental data on signal and noise characteristics of high--$T_c$ RF SQUIDs with large inductance of quantization loop are presented. The SQUIDs were produced by a thick--film HTS--technique of painting on the Y$_2$BaCuO$_5$ substrate. For the first time, a steady quantum interference was observed in RF SQUID with the inductance as large as $L_S=6.6$ nH, that is, 60 times higher than the fluctuation inductance $L_F\simeq10^{-10}H$ at the liquid nitrogen temperature T=77 K. A new method is offered to evaluate the sensitivity of RF SQUID with optimum inductance of the quantization loop.