Editing Condensed matter physics (section)

===Classical physics===
[[File:Heike Kamerlingh Onnes and Johannes Diderik van der Waals.jpg|thumb|upright|[[Heike Kamerlingh Onnes]] and [[Johannes van der Waals]] with the [[helium]] ''liquefactor'' at Leiden in 1908]]

One of the first studies of condensed states of matter was by [[People of England|English]] [[chemist]] [[Humphry Davy]], in the first decades of the nineteenth century. Davy observed that of the forty [[chemical element]]s known at the time, twenty-six had [[metal]]lic properties such as [[lustre (mineralogy)|lustre]], [[ductility]] and high electrical and thermal conductivity.<ref name=goodstein>{{cite journal|last1=Goodstein|first1=David|author1-link=David Goodstein|last2=Goodstein|first2=Judith|author2-link=Judith R. Goodstein|title=Richard Feynman and the History of Superconductivity|journal=Physics in Perspective|year=2000|volume=2|issue=1|url=http://web.njit.edu/~tyson/supercon_papers/Feynman_Superconductivity_History.pdf|access-date=7 April 2012|doi=10.1007/s000160050035|pages=30|bibcode=2000PhP.....2...30G|s2cid=118288008|archive-url=https://web.archive.org/web/20151117113759/https://web.njit.edu/~tyson/supercon_papers/Feynman_Superconductivity_History.pdf|archive-date=17 November 2015|url-status=dead}}</ref> This indicated that the atoms in [[John Dalton]]'s [[atomic theory]] were not indivisible as Dalton claimed, but had inner structure. Davy further claimed that elements that were then believed to be gases, such as [[nitrogen]] and [[hydrogen]] could be liquefied under the right conditions and would then behave as metals.<ref name=davy-1839>{{cite book |editor-last=Davy |editor-first = John |title=The collected works of Sir Humphry Davy: Vol. II |year=1839|publisher=Smith Elder & Co., Cornhill |url = https://archive.org/details/bub_gb_6WNKAAAAYAAJ |page=[https://archive.org/details/bub_gb_6WNKAAAAYAAJ/page/n34 22] }}</ref>{{NoteTag|Both hydrogen and nitrogen have since been liquified; however, ordinary liquid nitrogen and hydrogen do not possess metallic properties. Physicists [[Eugene Wigner]] and [[Hillard Bell Huntington]] predicted in 1935<ref name=metallic-hydrogen>{{cite journal |last=Silvera|first=Isaac F.|author2=Cole, John W. |title=Metallic Hydrogen: The Most Powerful Rocket Fuel Yet to Exist|journal=Journal of Physics|year=2010|volume=215|issue=1 |doi=10.1088/1742-6596/215/1/012194 |bibcode= 2010JPhCS.215a2194S |pages=012194 |url = http://nrs.harvard.edu/urn-3:HUL.InstRepos:9569212 |doi-access=free}}</ref> that a state [[metallic hydrogen]] exists at sufficiently high pressures (over 25 [[Pascal (unit)|GPa]]), but this has not yet been observed.}}

In 1823, [[Michael Faraday]], then an assistant in Davy's lab, successfully liquefied [[chlorine]] and went on to liquefy all known gaseous elements, except for nitrogen, hydrogen, and [[oxygen]].<ref name=goodstein /> Shortly after, in 1869, [[People of Ireland|Irish]] chemist [[Thomas Andrews (scientist)|Thomas Andrews]] studied the [[phase transition]] from a liquid to a gas and coined the term [[Critical point (thermodynamics)|critical point]] to describe the condition where a gas and a liquid were indistinguishable as phases,<ref name=thomasandrews>{{cite journal|last=Rowlinson|first=J. S.|title=Thomas Andrews and the Critical Point|journal=Nature|year=1969|volume=224|issue=8|doi=10.1038/224541a0|pages=541–543|bibcode= 1969Natur.224..541R|s2cid=4168392}}</ref> and [[Netherlands|Dutch]] physicist [[Johannes van der Waals]] supplied the theoretical framework which allowed the prediction of critical behavior based on measurements at much higher temperatures.<ref name=atkins>{{cite book|last1=Atkins|first1=Peter|last2=de Paula|first2=Julio|title=Elements of Physical Chemistry|year=2009|publisher=Oxford University Press|isbn=978-1-4292-1813-9}}</ref>{{rp|35–38}} By 1908, [[James Dewar]] and [[Heike Kamerlingh Onnes]] were successfully able to liquefy hydrogen and the then newly discovered [[helium]] respectively.<ref name=goodstein />

[[Paul Drude]] in 1900 proposed the first theoretical model for a classical [[electron]] moving through a metallic solid.<ref name=marvincohen2008 /> Drude's model described properties of metals in terms of a gas of free electrons, and was the first microscopic model to explain empirical observations such as the [[Wiedemann–Franz law]].<ref name="Kittel 1996">{{cite book|last=Kittel|first=Charles|title=[[Introduction to Solid State Physics]]|year=1996|publisher=John Wiley & Sons|isbn=978-0-471-11181-8}}</ref><ref name=Hoddeson-1992>{{cite book|last=Hoddeson|first=Lillian|title=Out of the Crystal Maze: Chapters from The History of Solid State Physics|year=1992|publisher=Oxford University Press|isbn=978-0-19-505329-6|url=https://books.google.com/books?id=WCpPPHhMdRcC&pg=PA29}}</ref>{{rp|27–29}} However, despite the success of [[Drude model|Drude's model]], it had one notable problem: it was unable to correctly explain the electronic contribution to the [[specific heat]] and magnetic properties of metals, and the temperature dependence of resistivity at low temperatures.<ref name=Kragh2002>{{cite book |last= Kragh |first= Helge |title= Quantum Generations: A History of Physics in the Twentieth Century |publisher= Princeton University Press |edition= Reprint |date= 2002 |isbn= 978-0-691-09552-3}}</ref>{{rp|366–368}}

In 1911, three years after helium was first liquefied, Onnes working at [[University of Leiden]] discovered [[superconductivity]] in [[mercury (element)|mercury]], when he observed the electrical resistivity of mercury to vanish at temperatures below a certain value.<ref name=vanDelft2010>{{cite journal|last=van Delft|first=Dirk|author2=Kes, Peter |title=The discovery of superconductivity|journal=Physics Today|date=September 2010|volume=63|issue=9|doi=10.1063/1.3490499|url=http://www.lorentz.leidenuniv.nl/history/cold/DelftKes_HKO_PT.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.lorentz.leidenuniv.nl/history/cold/DelftKes_HKO_PT.pdf |archive-date=2022-10-09 |url-status=live|access-date=7 April 2012|bibcode= 2010PhT....63i..38V|pages=38–43|doi-access=free}}</ref> The phenomenon completely surprised the best theoretical physicists of the time, and it remained unexplained for several decades.<ref name=Slichter-AIP-supercond>{{cite web|last=Slichter|first=Charles|title=Introduction to the History of Superconductivity|url=http://www.aip.org/history/mod/superconductivity/01.html|website=Moments of Discovery|publisher=American Institute of Physics|access-date=13 June 2012|archive-url=https://web.archive.org/web/20120515123519/http://www.aip.org/history/mod/superconductivity/01.html|archive-date=15 May 2012|url-status=dead}}</ref> [[Albert Einstein]], in 1922, said regarding contemporary theories of superconductivity that "with our far-reaching ignorance of the quantum mechanics of composite systems we are very far from being able to compose a theory out of these vague ideas."<ref name=Schmalian-2010>{{cite journal|last=Schmalian|first=Joerg|title=Failed theories of superconductivity|year=2010|arxiv=1008.0447|bibcode= 2010MPLB...24.2679S |doi= 10.1142/S0217984910025280|journal=Modern Physics Letters B|volume=24|issue=27|pages=2679–2691|s2cid=119220454}}</ref>