Talk:High-temperature superconductivity

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Relation to room-temperature superconductivity?

Crowdyour, you changed the intro section to say:

A consistent theory of cuprate compounds does not currently exist; ... interest in this field is beyond the goal of achieving the room-temperature superconductivity.

This is almost the opposite of what I wrote before. But I must admit that the intro was very unclear before and I took a guess at what the original author was trying to say.

How does high-temp SC compare to room-temp SC? Is one seeing more research than the other? Is room-temp more or less likely to happen?

I assumed that room-temp SC was unlikely, and therefore more research is going into "high" temp SC. But obviously someone who knows needs to clarify.

Also, "the" should not appear before "room-temperature superconductivity". (English)

Low temperature superconductors

It is not true that "low temperature superconductors" always needs liquid helium temperatures. Generically, "low temperature superconductors" are defined by not being "high temperature superconductors". This just means that they are described by the conventional BCS theory. For instance, magnesium diboride (MgB2) is the most recently discovered conventional superconductor, and it has a Tc of 35K. The BCS theory describes "phonon mediated" electron pairing. Although it cannot predict Tc, there are general arguments that say that Tc can not get above 30-35K.

Some contemporary hi-Tc theories try to invoke phonons, but there is no consensus on their applicability. The largest peice of evidence against phonons is the lack of "isotope effect", where Tc is proportional to the square root of the mass of the isotopic substitution element occuring at one particular doping level in YBaCuO (optimum doping). The extended BCS theory, which generalizes weak coupling phonons to stronger coupling, known as the Eliashberg theory, predicts that the exponent will not be exactly 1/2, but will be material dependent. —Preceding unsigned comment added by 24.86.198.146 (talk • contribs) 05:28, 26 November 2004

Theory

The current description of work on the subject is very narrow and inaccurate in a number of places. Most notably, the leading theories which are being pursued are not the ones mentioned. A proper treatment both from a historical and Popperian perspective is necessary to achieve credibility. While not an easy task, a balanced approach to describing currently active theories is necessary if the article is to achieve some degree of respectability.

Merge

This page should be merged with High-temperature superconductors 220.244.224.10 00:36, 16 Mar 2005 (UTC)

I disagree. FS of cuprates is an involved topic and thus deserve a separate and a detailed article.Condmatstrel (talk) 21:27, 18 December 2012 (UTC)

Hmm. Take a look, and you'll see that High-temperature superconductors is merely a redirect to this article, High-temperature superconductivity. So neither of these comments makes sense at the present time. I see there were some merging in 2004 and 2006. — Quondum 05:20, 19 December 2012 (UTC)

The content of Fermi surface of superconducting cuprates was merged into High-temperature superconductivity on 22 May 2016. The former page's history now serves to provide attribution for that content in the latter page, and it must not be deleted as long as the latter page exists. For the discussion at that location, see its talk page.

Hydrogen

Why it seems like there's no study on this together with the first element? --Cacumer 18:33, 3 February 2006 (UTC)

Superconductivity in Hydrogen was predicted about 40 years ago but the pressures required to test this hypothesis are still unavailable. The article now refers to this prediction. 78.86.83.92 (talk) 02:40, 25 January 2009 (UTC)

Naming

I've been out of the field for too long to make good contributions to this article. But "back in the day" I actively avoided the term "high temperature" to describe these materials. Yes, it's high compared to the Tc of Nb3Sn, but 100 Kelvin is not "high" in any absolute sense. What will we call the 200 K superconductors of the future? "Collosal High Temperature"? I propose "perovskite superconductors" or "cuprate superconductors", unless those terms have died out. Spiel496 23:30, 7 April 2006 (UTC)

The term "high-temperature superconductor" is definitely well established and current in this context --spiralhighway 00:07, 14 June 2006 (UTC)

I agree, the term "high-temperature superconductor" is a widely used term. Besides, high and low temperature is not meant to be an absolute scale. When studying neutron start, 10^8 K is a low temperature. The Kondo effect is a low temperature effect, and can occur around 400 K. Similarly, 100 K is a high temperature for superconductivity to occur. Also, I feel high-temperature superconductor is a better term than "perovskite superconductors" or "cuprate superconductors", since not all high-tc superconductors are perovskite or cuprates, take the ruthenates for example. PhysicsBob 13:32, 6 November 2007 (UTC)

Relativity. Measures can never be low or high in physics. They are relative to a reference point you stablish. A value is high or low only when it is compared to another value. They are "high-temperature superconductor" compared to actual semiconductors. The name is 'relatively' correct, hehe. —Preceding unsigned comment added by 217.216.195.163 (talk) 00:29, 2 September 2008 (UTC)

The three alternative definitions in the introduction (historical, physical, and technical) now attempt to clear up this issue. 78.86.83.92 (talk) 02:40, 25 January 2009 (UTC)

Surely it's "high" relative to the temperatures that BCS theory predicts? —Preceding unsigned comment added by 86.53.69.150 (talk) 00:20, 13 March 2010 (UTC)

Proposed restructuring + expanding

Maybe we can improve this article by introducing some sections to it. Here's my first cut at a proposal, please feel free to edit / change / add mercilessly:

• Background - mostly stuff that's already there
• Theory - contending theories, description of Anderson RVB model
• HTSC research overview - including the main motivations for it, what's known, the big outstanding questions
• Maybe 2 sections about specific research questions in the field
• Applications - applications of current HTSC materials
• Research groups - maybe a list of major research groups around the world and their fields of specialization

--James Slezak 01:15, 21 June 2006 (UTC)

I agree with this structure in principle, but perhaps the section on Research Groups could be dropped, since it wouldn't tell us much about high-tc superconductors. Also, I think the theory could be a bad idea, since it is probably one of the most contentious points in physics at the moment, and nobody seems to know really what they're doing. Conversely, it is a good idea since it will give readers an idea about what people think about high-tc at present. PhysicsBob 13:36, 6 November 2007 (UTC)

Materials

It seems that many of the materials listed are very out of date. Also, no mention of nanotubule research Dtsvaro 08:47, 30 July 2006 (UTC)

As I understand it, carbon nanotubes reach superconductivity at about 20K, making them low-temperature superconductors. YBCO was still the leading class of high-temp ceramics when I was working in a lab 3 years ago... I can't comment on advances since then. Garrepi 07:51, 17 August 2006 (UTC)

It appears that high temperature superconductivity early reports of CNT = carbon nano tubes has not been confirmed. Other types of nano tubes, perhaps. Ccpoodle 17:53, 22 July 2007 (UTC)

Dummy sections

I'm commenting these out. I assume they're being used as guidelines for future development, but the article needn't look like a skeleton in the interim. Chris Cunningham 10:49, 22 February 2007 (UTC)

bbc article about htsc

http://news.bbc.co.uk/2/hi/technology/6412057.stm

i think that's interesting and a good source. —The preceding unsigned comment was added by 80.133.226.122 (talk) 09:57, 6 March 2007 (UTC).

possible copyright infringement

Chapter 'How High-Temperature Superconductors are Made' seems to be very similar to the last chapter 'How does STI make its thin-film microelectronics, or microchips?' on http://www.suptech.com/tech_faq.htm 84.231.69.60 19:01, 28 June 2007 (UTC)

True. However, given how short the section is, I think we can get away with using it as a reference. It's not a 1:1 copy, although that's clearly where it was taken from. Thanks. Chris Cunningham 19:10, 28 June 2007 (UTC)

Pressure mounts for HTSC.

http://www.eetimes.com/news/latest/showArticle.jhtml;jsessionid=HTTOTGYXPCPWSQSNDLSCKHA?articleID=206904213 —Preceding unsigned comment added by 82.131.210.162 (talk) 11:38, 20 March 2008 (UTC)

split cuprate SC into separate article ?

At the moment the article is dominated by the original type of HTS. Copper oxide details could move into cuprate superconductors so we can have a more balanced summary of the other families here including fullerenes, MgB2 and now the oxypnictides. Rod57 (talk) 17:17, 14 June 2008 (UTC)

Improved sectioning of the article could achieve this aim. Nevertheless, far more is known about the cuprates than oxypnictides or fullerenes. The article should reflect this. 163.1.18.232 (talk) 23:55, 24 January 2009 (UTC)

I hope the resectioning into Cuprate, Iron-based superconductors, and Other has achieved this aim. Doktor Waf (talk) 01:09, 22 February 2009 (UTC)

Looks great. Rod57 (talk) 17:07, 12 December 2009 (UTC)

Just to bring to your attention that there is already a cuprate stub article which can be used for keeping some material. Materialscientist (talk) 00:19, 13 December 2009 (UTC)

subject: Feb 1987 YBCO discovered to have Tc of 90 K by Paul Chu et al.

This is in my opinion not correct. The original article is to my knowledge:

M. K. Wu, J. R. Ashburn, C. J. Torng, P. H. Hor, R. L. Meng, L. Gao, Z. J. Huang, Y. Q. Wang, and C. W. Chu
Superconductivity at 93 K in a new mixed-phase Y-Ba-Cu-O compound system at ambient pressure
Phys. Rev. Lett. 58, 908 - 910 (1987)

change it? —Preceding unsigned comment added by 141.20.202.78 (talk) 10:55, 29 June 2008 (UTC)

It was Paul (C.W.) Chu's research group who made the discovery. Naming the authors is probably extraneous now the correct reference is included. 163.1.18.232 (talk) 23:55, 24 January 2009 (UTC)

Comment by rcarden: With all due respect, the discovery was made by the UAHuntsville group who was NOT acting under Chu's direction. They enlisted the Houston group to perform additional magnetic measurements. Chu himself confirms this in “High-Temperature Superconducting Materials: A Decade of Impressive Advancement of Tc” (http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=614424):

I received an exciting call from M. K. [Wu] at about 5 pm, January 29, 1987. He informed me that he and his students had just observed a reversible R drop above 77K in two of their samples. All of us were ecstatic, since stable superconductivity above 77K might have finally been achieved. M. K. and his student, Jim Ashburn, decided to fly to Houston to carry out a definitive magnetic check with us. Without knowing the elements used in their samples, we tested a few samples, with La replaced by the newly arrived Y and Yb oxides. We failed to detect 90K superconductivity in these samples the night before their arrival. M. K. and Jim arrived late on the morning of January 30, with their samples, which had a nominal formula of (Y0.6Ba0.4)2CuO4 (YBCO). A thorough battery of resistive and magnetic tests (Fig. 4) in various fields showed the R drop M. K. observed to be superconductivity above 90K. Following the recipe of M. K., several more samples were immediately made in Houston and tested the same day. Most showed superconductivity up to 93K. The long sought stable superconductivity above 77K was discovered. — Preceding unsigned comment added by Russellcarden (talk • contribs) 19:32, 1 December 2011 (UTC)

Better than perpertual motion!

Whoever inserted that 185K claim link it looks like self-hype by a fringe american company and is probably as real as the milk jar cold fusion (i.e. bullshit). Those guys describe their actions as exactly as a housewife mixing ingredients for a soup... I think it should be removed. 82.131.210.162 (talk) 18:24, 15 July 2008 (UTC)

I have removed the 200K and 212K superconductors from the History and progress section. The results presented in the external links show only very small changes in bulk measurements that are not correlated between different techniques and are not significantly above the experimental noise. At best they might represent very small minority phases but have not been reported in peer-reviewed journals (like the other materials in the section) and there is no evidence presented for these measurements having been repeated independently. If these materials are reported as bulk superconductors in peer-reviewed journals then they would merit inclusion in this article. 163.1.18.232 (talk) 23:55, 24 January 2009 (UTC)

General phase diagram section

This section currently seems confused between the magnetic field - temperature phase diagram that characterizes the ordering of the superconducting vortex lattice, and the transition temperature - chemical doping phase diagram that defines the superconducting properties of cuprates or iron-based materials. These might be better discussed in separate sections. Since the doping phase diagram applies to all cuprates (and separate ones for other types of HTS) it should be the "General phase diagram". The vortex ordering diagram is not universal and applies equally well to layered materials that are not HTS. Figures like those referred to in the external links would also significantly improve this section. 78.86.83.92 (talk) 23:07, 24 January 2009 (UTC)

I have inserted phase diagrams into the cuprate and iron-based superconductors sections, and moved the discussion of the Type-II behaviour to the introduction - thereby making the General Phase Diagram section redundant. Now it is redundant I have removed it. Doktor Waf (talk) 01:09, 22 February 2009 (UTC)

Sun. Oct. 11th Nextbigfuture article about 254K superconductivity.

Looks like it is just a low volume measurement but it blows away all high temp superconductors in this article. Y3Ba5Cu8O18

http://nextbigfuture.com/2009/10/confirmation-of-ultra-ycbo.html —Preceding unsigned comment added by 99.23.163.109 (talk) 22:45, 12 October 2009 (UTC)

Also appeared on Slashdot. Is the guy behind this a crank, or not? It's hard for me to tell. The methods used correspond to things I've heard about during recent years of working in condensed matter physics, and none of the arguments used seem outside the bounds of my (limited) understand of superconductivity... but the site looks very amateurish, the claims are sensational, the figures are poorly labeled, and there are few references to other work, nor an obvious source of the funding necessary to do this kind of research. Moxfyre (ǝɹʎℲxoɯ | contrib) 03:37, 13 October 2009 (UTC)

This is a very major claim. If it was credible, it would be all over the news. Gruntler (talk) 03:46, 13 October 2009 (UTC)

And "Joe Eck" sounds a lot like "joke". Ken Arromdee (talk) 19:55, 14 October 2009 (UTC)

I'm not sure this 254K superconductor should be included on this page until there are more references or published scientific papers, there are none on arxiv, nature or any journal published by iop. —Preceding unsigned comment added by 78.86.215.3 (talk) 16:52, 24 October 2009 (UTC)

OK, maybe it needs to be said more strongly. I object to the inclusion of anything relating to this, even when properly hedged with phrases like "without being replicated." It is extremely likely that the claims are just wrong. I see no reason to include them in an encyclopedic treatment of high-Tc superconductivity. Here, there is potential harm in confusing readers. Exposing misinformation is nice but we're greatly enlarging the audience for this misinformation, without really portraying the flimsiness of these results in a way that's clear to a lay reader. Anyway, exposing incorrect science isn't what Wikipedia doesThere are a million people with fringy ideas out there and we don't clutter up science pages with them until they manage to convince a decent-sized section of the community that what they're doing has scientific merit. Gruntler (talk) 06:39, 31 October 2009 (UTC)

I was weighing for myself what is better - silencing or exposing the errors, and upon second though agreed with Gruntler - WP can't and shouldn't reveal all mistakes. Thank you. Materialscientist (talk) 06:45, 31 October 2009 (UTC)

Works for me. The Slashdot link gave me pause as a popsci-notable claim and the site was linked an a half dozen or so articles, but I can see pulling WP:ONEWAY and WP:WEIGHT on this. Variously reliable claims of this nature come up regularly enough that we can probably track down a source reporting that. - 2/0 (cont.) 17:09, 31 October 2009 (UTC)

any updates on this guy Joe Eck who claims superconductivity at 216°C..?? 186.185.49.187 (talk) 02:59, 11 February 2022 (UTC)

Wrong formula

From article:

As of 2009, the highest-temperature superconductor (at ambient pressure) is mercury thallium barium calcium copper oxide (HgBa2Ca2Cu3Ox), at 135 K and is held by a cuprate-perovskite material

Where is the Thallium? Link http://www.nature.com/doifinder/10.1038/365323a0 suggests the compound is HgBa2Ca2Cu3O8+δ. Yet the article Unconventional superconductor claims

As of 2009, the highest-temperature superconductor (at ambient pressure) is mercury thallium barium calcium copper oxide (Hg12Tl3Ba30Ca30Cu45O125), at 138 K and is held by a cuprate-perovskite material

Links disagree too, HgBa2Ca2Cu3O8 + δ by Tl substitution, vs. HgBa2Cam-1CumO2m+2+δ (m=1, 2, and 3) .

How about cleaning up by someone knowledgable? --12:07, 15 December 2009 (UTC) —Preceding unsigned comment added by 193.71.38.142 (talk)

Thallium is a typo or a copy/paste leftover from previous edits. Corrected. Thanks. HgBa2Ca2Cu3O8+δ seems the right composition. Materialscientist (talk) 12:36, 15 December 2009 (UTC)

The highest Tc of 138 K is also shared by the fluorinated HgBa2Ca2Cu3O8+δ compound (http://prb.aps.org/abstract/PRB/v63/i6/e064511) that, under 23 GPa, reaches the highest Tc up to date (january 2010) of 166 K (see Physica C: Superconductivity Volumes 408-410, August 2004, Pages 23-24 and http://www.iop.org/EJ/abstract/0295-5075/72/3/458) Please, include this info in the article. —Preceding unsigned comment added by 190.17.214.222 (talk) 17:16, 14 January 2010 (UTC)

This article has strong claims, but only 16 citations since 2001, although it was published in PRB (respectable journal). Thus I would not include it. I don't know reasons for low popularity, but some could be: (i) replacement of oxygen by fluorine is extremely impractical. (ii) the 4K increase is rather low and questionable, as it was observed in magnetization measurements (not in resistivity) which do not probe the conduction path, but may respond to disconnected superconducting regions. Also doping not just shifted the magnetization-temperature curve, but changed its shape. Materialscientist (talk) 07:54, 27 January 2010 (UTC)

Fermi temperature?

The article mentions "Fermi temperature" but links to Fermi level, an article that does not mention temperature at all. I don't pretend to understand any concept that starts with "Fermi" (I don't understand those articles; they appear written for physicists who already know the subject matter). But a reference that does not explain a technical concept is not acceptable in an encyclopedia. Can someone who understands the subject matter please fix this, or add an understandable definition of Fermi temperature? It would be nice to know the nature of the upper bound for HT superconductor temperatures, with some examples of actual values (of course, any future discovery of room-temperature SC will render my issue moot). David Spector 22:02, 25 February 2010 (UTC)

The Fermi temperature is equal to the conduction electrons' Fermi level (measured in eV) divided by the Boltzmann constant (measured in eV/K). At the Fermi temperature (which for most metals is extremely high, well above both the melting and boiling points and over 10000K), the conduction electrons would begin to follow Maxwell-Boltzmann statistics (i. e., behave classically) rather than Fermi-Dirac statistics. This is impossible to achieve in practice for metals (since such high temperatures would vaporize the metal). However, in some n-type semiconductors, the Fermi level of the electrons in the conduction band is small enough that the Fermi temperature becomes reachable, and may even be below room temperature. That's my understanding of how this works; hope that clears things up. Stonemason89 (talk) 14:22, 3 May 2010 (UTC)

Pseudogap "a new phase of matter"?

Recent paper:

• Ruihua He, Makoto Hashimoto, Hovnatan Karapetyan, Jake Koralek, Jamie Hinton, Jean-Pierre Testaud, Vikram Nathan, Yoshiyuki Yoshida, Hong Yao, Kiyohisa Tanaka, Worawat Meevasana, Rob Moore, Donhui Lu, Sung-Kwan Mo, Motoyuki Ishikado, Hiroshi Eisaki, Zahid Hussain, Thomas Devereaux, Steven Kivelson, Joseph Orenstein, Aharon Kapitulnik, and Zhi-Xun Shen (25 March 2011). "From a single-band metal to a high-temperature superconductor via two thermal phase transitions" (PDF). Science. 331: 1579–83. arXiv:1103.2363.{{cite journal}}: CS1 maint: multiple names: authors list (link)
• "Closing in on the pseudogap" (Press release). Lawrence Berkley Laboratory. 24 March 2011. Retrieved 25 March 2011.
• "High-temperature Superconductor Spills Secret: A New Phase of Matter" (Press release). SLAC National Linear Accelerator Laboratory, Stanford. 24 March 2011. Retrieved 25 March 2011.

LeadSongDog come howl! 20:37, 25 March 2011 (UTC)

No mention of PuCoGa5

Why is that? —Preceding unsigned comment added by 168.156.40.253 (talk) 20:06, 16 May 2011 (UTC)