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takeoff_speed:continuity_of_progress:historic_trends_in_the_maximum_superconducting_temperature [2022/09/21 07:37] (current) |
| ====== Historic trends in the maximum superconducting temperature ====== |
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| // Published 07 February, 2020; last updated 28 May, 2020 // |
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| <p>The maximum superconducting temperature of any material up to 1993 contained four greater than 10-year discontinuities: A 14-year discontinuity with NbN in 1941, a 26-year discontinuity with LaBaCuO4 in 1986, a 140-year discontinuity with YBa2Cu3O7 in 1987, and a 10-year discontinuity with BiCaSrCu2O9 in 1987.</p> |
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| <p>YBa2Cu3O7 superconductors seem to correspond to a marked change in the rate of progress of maximum superconducting temperature, from a rate of progress of .41 Kelvin per year to a rate of 5.7 Kelvin per year.</p> |
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| ===== Details ===== |
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| <p>This case study is part of AI Impacts’ <a href="/doku.php?id=ai_timelines:discontinuous_progress_investigation">discontinuous progress investigation</a>.</p> |
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| ==== Background ==== |
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| <p>Superconductors were discovered in 1911.<span class="easy-footnote-margin-adjust" id="easy-footnote-1-1618"></span><span class="easy-footnote"><a href="#easy-footnote-bottom-1-1618" title="&#8220;Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic flux fields occurring in certain materials, called superconductors, when cooled below a characteristic critical temperature. It was discovered by Dutch physicist Heike Kamerlingh Onnes on April 8, 1911, in Leiden.&#8221; &#8211; &#8220;Superconductivity&#8221;. 2018.&nbsp;<em>En.Wikipedia.Org</em>. Accessed June 29 2019. https://en.wikipedia.org/w/index.php?title=Superconductivity&amp;oldid=903681858."><sup>1</sup></a></span> Until 1986 the maximum temperature for superconducting behavior had gradually risen from around 4K to less than 30K (see figure 2 below). Theory at the time apparently predicted that 30K was an upper limit.<span class="easy-footnote-margin-adjust" id="easy-footnote-2-1618"></span><span class="easy-footnote"><a href="#easy-footnote-bottom-2-1618" title='&#8220;Until 1986 it was thought that superconducting behaviour was confined to certain materials at temperatures below ~30 K. A theory called “BCS theory” after its creators John Bardeen, Leon Cooper and Robert Schrieffer had been formulated to describe superconductivity. This theory, for which its creators received the Nobel Prize in Physics in 1972, appeared to back this up but put a limit on the critical temperature of around 30 K.&#8221; &#8211;<a href="https://en.wikipedia.org/wiki/Yttrium_barium_copper_oxide">I</a>&#8220;Doitpoms &#8211; TLP Library Superconductivity &#8211; Discovery And Properties&#8221;. 2019.&nbsp;<em>Doitpoms.Ac.Uk</em>. Accessed June 29 2019. https://www.doitpoms.ac.uk/tlplib/superconductivity/discovery.php.'><sup>2</sup></a></span> In 1986 a new class of ceramics known as YBCO superconductors was discovered to allow superconducting behavior at higher temperatures: above 80K,<span class="easy-footnote-margin-adjust" id="easy-footnote-3-1618"></span><span class="easy-footnote"><a href="#easy-footnote-bottom-3-1618" title="&#8220;Yttrium barium copper oxide (YBCO) is a family of crystalline chemical compounds, famous for displaying high-temperature superconductivity. It includes the first material ever discovered to become superconducting above the boiling point of liquid nitrogen (77 K) at about 92 K.&#8221; &#8211; &#8220;Yttrium Barium Copper Oxide&#8221;. 2019.&nbsp;<em>En.Wikipedia.Org</em>. Accessed June 29 2019. https://en.wikipedia.org/w/index.php?title=Yttrium_barium_copper_oxide&amp;oldid=903757351."><sup>3</sup></a></span> and within seven years, above 130K.<span class="easy-footnote-margin-adjust" id="easy-footnote-4-1618"></span><span class="easy-footnote"><a href="#easy-footnote-bottom-4-1618" title="&#8220;Here we provide support for this conjecture, with the discovery of superconductivity above 130 K in a material containing HgBa<sub>2</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>1+x</sub>&nbsp;(with three CuO<sub>2</sub>&nbsp;layers per unit cell), HgBa<sub>2</sub>CaCu<sub>2</sub>O<sub>6+x</sub>&nbsp;(with two CuO< |