Editing SQUID (section)

=== Materials used ===
The traditional [[superconducting]] materials for SQUIDs are pure [[niobium]] or a lead [[alloy]] with 10% gold or [[indium]], as pure lead is unstable when its temperature is repeatedly changed. To maintain superconductivity, the entire device needs to operate within a few degrees of [[absolute zero]], cooled with [[liquid helium]].<ref>{{cite journal |last1=Clarke |first1=John |title=SQUIDs |journal=Scientific American |date=August 1994 |volume=271 |issue=2 |pages=46–53 |doi=10.1038/scientificamerican0894-46 |jstor=24942801 |bibcode=1994SciAm.271b..46C |url=https://www.jstor.org/stable/24942801 |access-date=18 August 2022}}</ref>

High-temperature SQUID sensors were developed in the late 1980s.<ref>M.S. Colclough, C.E. Gough et al, Radiofrequency SQUID operation usinga ceramic high temperature superconductor,  Nature 328, 47 (1987)</ref> They are made of [[High-temperature superconductivity|high-temperature superconductors]], particularly [[yttrium barium copper oxide|YBCO]], and are cooled by [[liquid nitrogen]] which is cheaper and more easily handled than liquid helium. They are less sensitive than conventional low temperature SQUIDs but good enough for many applications.<ref>LP Lee et al., Monolithic 77K DC SQUID magnetometer, Applied Physics Letters 59, 3051 (1991)</ref>

In 2006, A proof of concept was shown for CNT-SQUID sensors built with an aluminium loop and a single walled [[carbon nanotube]] Josephson junction.<ref>{{Cite journal | last1 = Cleuziou | first1 = J.-P. | last2 = Wernsdorfer | first2 = W. | doi = 10.1038/nnano.2006.54 | title = Carbon nanotube superconducting quantum interference device | journal = Nature Nanotechnology | volume = 1 | issue = October | pages = 53–59| year = 2006 | pmid =  18654142|bibcode =  2006NatNa...1...53C| s2cid = 1942814 }}</ref> The sensors are a few 100&nbsp;nm in size and operate at 1K or below. Such sensors allow to count spins.<ref>{{Cite journal | last1 = Aprili | first1 = Marco | doi = 10.1038/nnano.2006.78 | title = The nanoSQUID makes its debut | journal = Nature Nanotechnology | volume = 1 | issue = October | pages = 15–16| year = 2006 | pmid =  18654132|bibcode =2006NatNa...1...15A | s2cid = 205441987 }}</ref>

In 2022 a SQUID was constructed on [[Twistronics|magic angle twisted bilayer graphene (MATBG)]]<ref>{{Cite journal |last1=Portolés |first1=Elías |last2=Iwakiri |first2=Shuichi |last3=Zheng |first3=Giulia |last4=Rickhaus |first4=Peter |last5=Taniguchi |first5=Takashi |last6=Watanabe |first6=Kenji |last7=Ihn |first7=Thomas |last8=Ensslin |first8=Klaus |last9=de Vries |first9=Folkert K. |date=24 October 2022 |title=A tunable monolithic SQUID in twisted bilayer graphene |url=https://www.nature.com/articles/s41565-022-01222-0 |journal=Nature Nanotechnology |language=en |volume=17 |issue=11 |pages=1159–1164 |doi=10.1038/s41565-022-01222-0 |pmid=36280761 |arxiv=2201.13276 |bibcode=2022NatNa..17.1159P |s2cid=246430218 |issn=1748-3395}}</ref><ref>{{Cite web |title=A new quantum component made from graphene |url=https://ethz.ch/en/news-and-events/eth-news/news/2022/11/a-new-quantum-component-made-from-graphene.html |access-date=2022-11-15 |website=ethz.ch |date=3 November 2022 |language=en}}</ref>