I had the tab open and everything, and still somehow forgot to include a link to John Baez's blog post reporting on a talk by Tony Leggett which directly addresses some of the questions asked about yesterday's superconductivity post. It's about a talk called "Cuprate superconductivity: the current state of play" ("state of play" apparently being a favorite phrase of Leggett's), and directly addresses what's weird about high-temperature superconductors and why they haven't been explained theoretically.
These are notes from a talk, and thus somewhat compressed, but it's a good summary of the situation. Leggett is surprisingly optimistic, too, giving a 50% chance that some students alive today will see room-temperature superconductors in their lifetime.
- Log in to post comments
"State of play" is a term used in cricket for the progress of a match at some intermediate point. "At tea on the first day, India are 381 for 4" is an example. Given that cricket matches can last five days, Tony's use of the term for the 34-year quest to explain cuprate superconductivity strikes me as apt
WA Little, Phys. Rev. 134 A1416-A1424 (1964)
Exciton-based ambient temp supercons: polyacetylenes substituted with polarizable chromophores, [-C(Ar)=(Ar)C-]n or [=C(Ar)-(Ar)C=]n. Replace BCS large mass phonons (Debye temperature) with small mass excitons (energies around 2 eV or 23,000 K). Critical temps above 300 K are likely, even with weak coupling.
Little proposed pendant dyes and had no synthetic entry to the polyacteylenes. 55 years later, synthesis should be facile:
[ArH -> ArCHO --> ArCH(OH)-(C=O)Ar --> O=C(Ar)-(Ar)C=O] --> H2C=C(Ar)-(Ar)C=CH2 --> [=C(Ar)-(Ar)C=]n + H2C=CH2
Append long alkyl, PEO, or PPO chains to the monomer for solubility and lyotropic liquid crystal formation.
Current Organic Synthesis 2(2) 231 2005
Methylenation review
http://en.wikipedia.org/wiki/Olefin_metathesis
"Recent Advances in ADMET Polymerization" "Advances in Polymer Science" M Buchmeiser, Ed., 176 1-42 (2005)
Acyclic diene metathesis (ADMET) reviews
http://www.mazepath.com/uncleal/pave1.png
Stereogram hydrogens and pi bonds omitted for clarity. Supercons must not be chiral or electron conjugate momenta won't couple.
The 22-mer is apparently stabilized by -29.7 kcal/mole-arene. Dope with holes (iodine; organic strong Lewis acid oxidizer) or electrons (alkali metal; organic strong Lewis base reductant) to set it off.
Somebody should look. The worst it can do is succeed.