Editing High-temperature superconductivity (section)

== History ==
[[File:Timeline of Superconductivity from 1900 to 2015.svg|thumb|upright=2|Timeline of superconductor discoveries. On the right one can see the liquid nitrogen temperature, which usually divides superconductors at high from superconductors at low temperatures. [[Cuprate]]s are displayed as blue diamonds, and [[iron-based superconductor]]s as yellow squares. [[Magnesium diboride]] and other low-temperature or high-pressure metallic [[BCS superconductor]]s are displayed for reference as green circles.]]

Superconductivity was discovered by [[Heike Kamerlingh Onnes|Kamerlingh Onnes]] in 1911, in a metal solid. Ever since, researchers have attempted to create superconductivity at higher temperatures<ref name="bbc">{{cite video |people=Nisbett, Alec (producer) |year=1988 |title=Superconductor: The race for the prize |medium=Television Episode}}</ref> with the goal of finding a [[room-temperature superconductor]].<ref>{{cite book |last=Mourachkine|first=A. |year=2004 |title=Room-Temperature Superconductivity |publisher=Cambridge International Science Publishing |arxiv=cond-mat/0606187 |place=Cambridge, UK |id=cond–mat/0606187|isbn=1-904602-27-4|bibcode=2006cond.mat..6187M}}</ref> By the late 1970s, superconductivity was observed in several metallic compounds (in particular [[Niobium|Nb]]-based, such as [[Niobium–titanium|NbTi]], [[Niobium–tin|Nb<sub>3</sub>Sn]], and [[Nb3Ge|Nb<sub>3</sub>Ge]]) at temperatures that were much higher than those for elemental metals and which could even exceed {{convert|20|K|C}}.

In 1986, at the [[IBM]] research lab near [[Zürich]] in Switzerland, Bednorz and Müller were looking for superconductivity in a new class of [[ceramic]]s: the copper oxides, or [[cuprates]]. In that year, [[Johannes Georg Bednorz|Bednorz]] and Müller discovered superconductivity in [[lanthanum barium copper oxide]] (LBCO), a [[lanthanum]]-based cuprate [[Perovskite (structure)|perovskite]] material, which had a transition temperature of 35&nbsp;K (Nobel Prize in Physics, 1987).<ref name="Bednorz">{{cite journal |author=Bednorz |first1=J. G. |last2=Müller |first2=K. A. |name-list-style=amp |date=1986 |title=Possible high T<sub>c</sub> superconductivity in the Ba−La−Cu−O system |journal=Z. Phys. B |volume=64 |issue=1 |pages=189–193 |bibcode=1986ZPhyB..64..189B |doi=10.1007/BF01303701 |s2cid=118314311}}</ref> It was soon found that replacing the lanthanum with [[yttrium]] (i.e.,&nbsp;making YBCO) raised the critical temperature above 90&nbsp;K.<ref name="wu">{{cite journal |author=Wu |first=M. K. |display-authors=etal |date=1987 |title=Superconductivity at 93 K in a New Mixed-Phase Y–Ba–Cu–O Compound System at Ambient Pressure |journal=[[Physical Review Letters]] |volume=58 |issue=9 |pages=908–910 |bibcode=1987PhRvL..58..908W |doi=10.1103/PhysRevLett.58.908 |pmid=10035069 |doi-access=free}}</ref> Their results were soon confirmed<ref>{{cite book|editor-first1=Stuart A.|editor-last1=Wolf|editor-first2=Vladimir Z.|editor-last2=Kresin|title=Novel Superconductivity|location=New York|publisher=Plenum Press|orig-year=1987|date=6 December 2012|isbn=978-1-4613-1937-5|url={{GBurl|9KfSBwAAQBAJ}}|access-date=2 August 2023}}</ref> by many groups.<ref name="tanaka01">
{{cite journal
 |last=Tanaka |first=Shoji
 |title=High temperature superconductivity: History and Outlook
 |journal=JSAP International
 |year=2001
 |url=http://www.jsap.or.jp/jsapi/Pdf/Number04/PastPresentFuture.pdf
 |access-date=March 2, 2012|url-status=live
 |archive-url=https://web.archive.org/web/20120816203010/http://www.jsap.or.jp/jsapi/Pdf/Number04/PastPresentFuture.pdf
 |archive-date=August 16, 2012
}}
</ref>

In 1987, [[Philip W. Anderson]] gave the first theoretical description of these materials, based on the [[resonating valence bond theory|resonating valence bond (RVB) theory]],<ref name=Anderson87>
{{cite journal
 |last=Anderson |first=Philip
 |year=1987
 |title=The Resonating Valence Bond State in La<sub>2</sub>CuO<sub>4</sub> and Superconductivity
 |journal=Science
 |volume=235 |issue=4793 |pages=1196–1198
 |bibcode=1987Sci...235.1196A |doi=10.1126/science.235.4793.1196
 |pmid=17818979 |s2cid=28146486
}}
</ref> but a full understanding of these materials is still developing today. These superconductors are now known to possess a ''d''-wave{{clarify|date=June 2014}} pair symmetry. The first proposal that high-temperature cuprate superconductivity involves ''d''-wave pairing was made in 1987 by N. E. Bickers, [[Douglas James Scalapino]] and R. T. Scalettar,<ref name=bickers87>
{{cite journal
 |last1=Bickers    |first1=N. E.
 |last2=Scalapino  |first2=D. J.
 |last3=Scalettar  |first3=R. T.
 |year=1987
 |title=CDW and SDW mediated pairing interactions
 |journal=Int. J. Mod. Phys. B
 |volume=1|issue=3n04|pages=687–695
 |bibcode=1987IJMPB...1..687B|doi=10.1142/S0217979287001079
}}
</ref> followed by three subsequent theories in 1988 by Masahiko Inui, Sebastian Doniach, Peter J. Hirschfeld and Andrei E. Ruckenstein,<ref name=inui88>
{{cite journal |last1=Inui |first1=Masahiko|last2=Doniach |first2=Sebastian |last3=Hirschfeld |first3=Peter J.|last4=Ruckenstein |first4=Andrei E. |last5=Zhao |first5=Z. |last6=Yang |first6=Q. |last7=Ni |first7=Y. |last8=Liu |first8=G. |year=1988 |title=Coexistence of antiferromagnetism and superconductivity in a mean-field theory of high-{{mvar|T}}{{sub|c}} superconductors |journal=Phys. Rev. B |volume=37 |issue=10 |pages=5182–5185 |bibcode=1988PhRvB..37.5182D|doi=10.1103/PhysRevB.37.5182|pmid=9943697 |url=http://prb.aps.org/abstract/PRB/v37/i4/p2320_1|url-status=dead |archive-url=https://archive.today/20130703172401/http://prb.aps.org/abstract/PRB/v37/i4/p2320_1 |archive-date=July 3, 2013}}</ref> using spin-fluctuation theory, and by [[Claudius Gros]], Didier Poilblanc, Maurice T. Rice and FC. Zhang,<ref name=gros88>
{{cite journal
 |last1=Gros   |first1=Claudius
 |last2=Poilblanc |first2=Didier
 |last3=Rice   |first3=T. Maurice|author3-link=Thomas Maurice Rice
 |last4=Zhang  |first4=F. C. |author4-link=Zhang Fuchun
 |year=1988
 |title=Superconductivity in correlated wavefunctions
 |journal=Physica C
 |volume=153–155 |pages=543–548
 |bibcode=1988PhyC..153..543G |doi=10.1016/0921-4534(88)90715-0
}}</ref> and by [[Gabriel Kotliar]] and Jialin Liu identifying ''d''-wave pairing as a natural consequence of the RVB theory.<ref name=kotliar88>
{{cite journal
 |last1=Kotliar |first1=Gabriel
 |last2=Liu     |first2=Jialin
 |year=1988
 |title=Superexchange mechanism and d-wave superconductivity
 |journal=Physical Review B
 |volume=38 |issue=7 |pages=5142–5145
 |bibcode=1988PhRvB..38.5142K |doi=10.1103/PhysRevB.38.5142 |pmid=9946940
}}
</ref> The confirmation of the ''d''-wave nature of the cuprate superconductors was made by a variety of experiments, including the direct observation of the ''d''-wave nodes in the excitation spectrum through [[Angle-resolved photoemission spectroscopy|angle resolved photoemission spectroscopy]] (ARPES), the observation of a half-integer flux in tunneling experiments, and indirectly from the temperature dependence of the penetration depth, specific heat and thermal conductivity.

Until 2001 the cuprates were thought be the only true high temperature superconductors. In that year MgB<sub>2</sub> with T<sub>c</sub> of 39K was discovered by Akimitsu and colleagues. This was followed in 2006 by Hosono and coworkers with iron-based layered  [[oxypnictide]] compound with T<sub>c</sub> of 56K.<ref>{{Cite journal |last=Kamihara |first=Yoichi |last2=Hiramatsu |first2=Hidenori |last3=Hirano |first3=Masahiro |last4=Kawamura |first4=Ryuto |last5=Yanagi |first5=Hiroshi |last6=Kamiya |first6=Toshio |last7=Hosono |first7=Hideo |date=2006-08-01 |title=Iron-Based Layered Superconductor:  LaOFeP |url=https://pubs.acs.org/doi/10.1021/ja063355c |journal=Journal of the American Chemical Society |volume=128 |issue=31 |pages=10012–10013 |doi=10.1021/ja063355c |issn=0002-7863}}</ref> These temperature are below the cuprates but well above the conventional superconductors.<ref name=Bussman-Holder-2020>{{Cite journal |last=Bussmann-Holder |first=Annette |last2=Keller |first2=Hugo |date=2020-02-01 |title=High-temperature superconductors: underlying physics and applications |url=https://www.degruyterbrill.com/document/doi/10.1515/znb-2019-0103/html |journal=Zeitschrift für Naturforschung B |language=en |volume=75 |issue=1-2 |pages=3–14 |doi=10.1515/znb-2019-0103 |issn=1865-7117|arxiv=1911.02303 }}</ref>

In 2014, evidence showing that fractional particles can happen in quasi two-dimensional magnetic materials was reported by [[École Polytechnique Fédérale de Lausanne]] (EPFL) scientists<ref>
{{cite journal
 |last1=Dalla Piazza |first1=B. |last2=Mourigal |first2=M.
 |last3=Christensen |first3=N. B. |last4=Nilsen |first4=G. J.
 |last5=Tregenna-Piggott |first5=P. |last6=Perring |first6=T. G.
 |last7=Enderle |first7=M. |last8=McMorrow |first8=D. F.
 |last9=Ivanov |first9=D. A. |last10=Rønnow |first10=H. M.
 |display-authors=6
 |year=2015
 |title=Fractional excitations in the square-lattice quantum antiferromagnet
 |journal=Nature Physics
 |volume=11|issue=1|pages=62–68
 |doi=10.1038/nphys3172|pmid=25729400|pmc=4340518|arxiv=1501.01767
 |bibcode=2015NatPh..11...62D
}}
</ref> lending support for Anderson's theory of high-temperature superconductivity.<ref>
{{cite press release
 |title=How electrons split: New evidence of exotic behaviors
 |date=December 23, 2014
 |website=Nanowerk
 |publisher=École Polytechnique Fédérale de Lausanne
 |url=http://www.nanowerk.com/nanotechnology-news/newsid=38557.php
 |access-date=December 23, 2014|url-status=live
 |archive-url=https://web.archive.org/web/20141223224211/http://www.nanowerk.com/nanotechnology-news/newsid=38557.php
 |archive-date=December 23, 2014
}}
</ref> In 2014 and 2015, [[hydrogen sulfide]] ({{chem|H|2|S}}) at extremely high pressures (around 150 gigapascals) was first predicted and then confirmed to be a high-temperature superconductor with a transition temperature of 80&nbsp;K.<ref>{{Cite journal |last1=Li |first1=Yinwei |last2=Hao |first2=Jian |last3=Liu |first3=Hanyu |last4=Li |first4=Yanling |last5=Ma |first5=Yanming |date=2014-05-07 |title=The metallization and superconductivity of dense hydrogen sulfide |journal=The Journal of Chemical Physics |volume=140 |issue=17 |pages=174712 |arxiv=1402.2721 |bibcode=2014JChPh.140q4712L |doi=10.1063/1.4874158 |issn=0021-9606 |pmid=24811660 |s2cid=15633660}}</ref><ref name="DrozdovEremets2015">{{cite journal |last1=Drozdov |first1=A. P. |last2=Eremets |first2=M. I. |last3=Troyan |first3=I. A. |last4=Ksenofontov |first4=V. |last5=Shylin |first5=S. I. |year=2015 |title=Conventional superconductivity at 203 kelvin at high pressures in the sulfur hydride system |journal=Nature |volume=525 |issue=7567 |pages=73–6 |arxiv=1506.08190 |bibcode=2015Natur.525...73D |doi=10.1038/nature14964 |issn=0028-0836 |pmid=26280333 |s2cid=4468914}}</ref><ref name=":02">{{Cite web |last=Wood |first=Charlie |date=14 October 2020 |title=Room-Temperature Superconductivity Achieved for the First Time |url=https://www.quantamagazine.org/physicists-discover-first-room-temperature-superconductor-20201014/ |access-date=2020-10-29 |website=Quanta Magazine |language=en}}</ref> 

In 2018, a research team from the Department of Physics, [[Massachusetts Institute of Technology]], discovered [[Bilayer graphene#Superconductivity in twisted bilayer graphene|superconductivity in bilayer graphene]] with one layer [[Twistronics|twisted at an angle]] of approximately 1.1&nbsp;degrees with cooling and applying a small electric charge. Even if the experiments were not carried out in a high-temperature environment, the results are correlated less to classical but high temperature superconductors, given that no foreign atoms needed to be introduced.<ref>{{Cite journal |last1=Cao |first1=Yuan |author-link1=Yuan Cao |last2=Fatemi |first2=Valla |last3=Demir |first3=Ahmet |last4=Fang |first4=Shiang |last5=Tomarken |first5=Spencer L. |last6=Luo |first6=Jason Y. |last7=Sanchez-Yamagishi |first7=J. D. |last8=Watanabe |first8=K. |last9=Taniguchi |first9=T. |date=2018-03-05 |title=Correlated insulator behaviour at half-filling in magic-angle graphene superlattices |journal=Nature |language=En |volume=556 |issue=7699 |pages=80–84 |arxiv=1802.00553 |bibcode=2018Natur.556...80C |doi=10.1038/nature26154 |issn=1476-4687 |pmid=29512654 |s2cid=4601086}}</ref> The superconductivity effect came about as a result of electrons twisted into a vortex between the graphene layers, called "[[Skyrmion|skyrmions]]". These act as a single particle and can pair up across the graphene's layers, leading to the basic conditions required for superconductivity.<ref>{{Cite web |last=Wood |first=Charlie |date=16 March 2021 |title=A New Twist Reveals Superconductivity's Secrets |url=https://www.quantamagazine.org/graphenes-new-twist-reveals-superconductivitys-secrets-20210316/ |access-date=2021-03-23 |website=Quanta Magazine |language=en}}</ref>

In 2019 it was discovered that [[lanthanum hydride]] ({{chem|La|H|10}}) becomes a superconductor at 250&nbsp;K under a pressure of 170 gigapascals.<ref>{{cite journal |last1=Drozdov |first1=A. P. |last2=Kong |first2=P. P. |last3=Minkov |first3=V. S. |last4=Besedin |first4=S. P. |last5=Kuzovnikov |first5=M. A. |last6=Mozaffari |first6=S. |last7=Balicas |first7=L. |last8=Balakirev |first8=F. F. |last9=Graf |first9=D. E. |last10=Prakapenka |first10=V. B. |last11=Greenberg |first11=E. |last12=Knyazev |first12=D. A. |last13=Tkacz |first13=M. |last14=Eremets |first14=M. I. |year=2019 |title=Superconductivity at 250 K in Lanthanum Hydride under High Pressures |journal=Nature |volume=569 |issue=7757 |pages=528–531 |arxiv=1812.01561 |bibcode=2019Natur.569..528D |doi=10.1038/s41586-019-1201-8 |pmid=31118520 |s2cid=119231000}}</ref><ref name=":02" />

In 2020, a [[room-temperature superconductor]] (critical temperature 288&nbsp;K) made from hydrogen, carbon and sulfur under pressures of around 270 gigapascals was described in a paper in ''Nature''.<ref>{{cite journal |last1=Snider |first1=Eliot |display-authors=etal |date=Oct 14, 2020 |title=Room-temperature superconductivity in a carbonaceous sulfur hydride |url=https://www.osti.gov/biblio/1673473 |journal=Nature |volume=586 |issue=7829 |pages=373–377 |bibcode=2020Natur.586..373S |doi=10.1038/s41586-020-2801-z |osti=1673473 |pmid=33057222 |s2cid=222823227}}{{Retracted|doi=10.1038/s41586-022-05294-9|pmid=36163290|intentional=yes}}</ref><ref>{{cite news |author=Chang |first=Kenneth |date=October 14, 2020 |title=Finally, the First Room-Temperature Superconductor |url=https://www.nytimes.com/2020/10/14/science/superconductor-room-temperature.html |newspaper=The New York Times}}</ref> However, in 2022 the article was [[Retraction in academic publishing|retracted]] by the editors because the validity of background subtraction procedures had been called into question. All nine authors maintain that the raw data strongly support the main claims of the paper.<ref>{{cite journal |last1=Snider |first1=Elliot |last2=Dasenbrock-Gammon |first2=Nathan |last3=McBride |first3=Raymond |last4=Debessai |first4=Mathew |last5=Vindana |first5=Hiranya |last6=Vencatasamy |first6=Kevin |last7=Lawler |first7=Keith V. |last8=Salamat |first8=Ashkan |last9=Dias |first9=Ranga P. |date=26 September 2022 |title=Retraction Note: Room-temperature superconductivity in a carbonaceous sulfur hydride |journal=Nature |volume=610 |issue=7933 |page=804 |bibcode=2022Natur.610..804S |doi=10.1038/s41586-022-05294-9 |pmid=36163290 |s2cid=252544156 |doi-access=free}}</ref>

In 2023 a study reported superconductivity at room temperature and ambient pressure in [[highly oriented pyrolytic graphite]] with dense arrays of nearly parallel line defects.<ref>{{cite journal |last1=Kopelevich |first1=Yakov |last2=Torres |first2=José |last3=Da Silva |first3=Robson |last4=Oliveira |first4=Felipe |last5=Diamantini |first5=Maria Cristina |last6=Trugenberger |first6=Carlo |last7=Vinokur |first7=Valerii |date=2024 |title=Global Room-Temperature Superconductivity in Graphite |url=https://onlinelibrary.wiley.com/doi/10.1002/qute.202300230?ref=upstract.com |journal=Advanced Quantum Technologies |volume=7 |issue=2 |arxiv=2208.00854 |doi=10.1002/qute.202300230}}</ref>

As of 2021,<ref name="cao21" /> the superconductor with the highest transition temperature at [[ambient pressure]] was the cuprate of mercury, barium, and calcium, at around {{cvt|133|K|C}}.<ref name="schilling93">
{{cite journal |last1=Schilling |first1=A. |last2=Cantoni |first2=M. |last3=Guo |first3=J. D. |last4=Ott |first4=H. R. |year=1993 |title=Superconductivity in the Hg–Ba–Ca–Cu–O system |journal=Nature |volume=363 |issue=6424 |pages=56–58 |bibcode=1993Natur.363...56S |doi=10.1038/363056a0 |s2cid=4328716}}
</ref> Other superconductors have higher recorded transition temperatures{{snd}}for example lanthanum superhydride at {{cvt|250|K|C}}, but these only occur at high pressure.<ref name="eremets">
{{cite journal |last1=Drozdov |first1=A. P. |last2=Kong |first2=P. P. |last3=Minkov |first3=V. S. |last4=Besedin |first4=S. P. |last5=Kuzovnikov |first5=M. A. |last6=Mozaffari |first6=S. |last7=Balicas |first7=L. |last8=Balakirev |first8=F. F. |last9=Graf |first9=D. E. |last10=Prakapenka |first10=V. B. |last11=Greenberg |first11=E. |last12=Knyazev |first12=D. A. |last13=Tkacz |first13=M. |last14=Eremets |first14=M. I. |year=2019 |title=Superconductivity at 250&nbsp;K in lanthanum hydride under high pressures |journal=Nature |volume=569 |issue=7757 |pages=528–531 |arxiv=1812.01561 |bibcode=2019Natur.569..528D |doi=10.1038/s41586-019-1201-8 |pmid=31118520 |s2cid=119231000}}
</ref>