Types of Superconductors  

In General
* Type I, < : Positive wall energy; not so useful, can't be used for magnets.
* Type II, > : Negative wall energy, maximize surface and create vortices, quantized in units of B = hc/2e; Includes all high-Tc.
* BCS vs Unconventional (non-BCS):
* Examples: The heavy fermion compound UPt3.
@ Examples: news pw(02)jan; Canfield & Bud'ko SA(05)apr [MgB2].

High-Temperature Superconductivity > s.a. Insulators.
* History: 1986, Discovery and almost immediate hopes for room-temperature superconductors; 2004, Still not completely understood and no Tc's near room temperature.
* Properties: Usually very anisotropic (the energy gap is direction-dependent).
* Mechanism: 2004, It is widely believed that the classic BCS theory cannot explain it; Cooper pairs are involved but it is not clear what holds them together; There are claims that interactions between phonons and electrons or magnetic resonances are relevant, but recent experiments seem to rule those explanations out; 2008, Electron-phonon interactions can only account for a fraction of the behaviour.
* Examples: The most common one by far is YBCO (YBa2Cu3O7).
@ Books, reviews: Ginzburg SPU(91) [rev]; Holton et al AS(96) [discovery]; Nowotny & Felt 02 [r PT(98)mar].
@ News: Maddox Nat(90)apr; Hamilton Sci(90)oct [Tc = 125 K]; pw(06)aug [evidence for role of phonons]; pw(06)sep [decline in number of publications]; pn(07)jul [and Mott insulator properties]; PT(08)jan [use on the power grid]; pw(08)apr [not explained by phonons].
@ Theory: Davydov PRP(90); Kulic PRP(00); Lanzara et al Nat(01)aug [phonon-electron]; Herbut PRL(05)cm/04 [effective theory].

In Particle Physics and Field Theory > s.a. cosmic strings [superconducting]; QCD [vacuum].
@ Color superconductivity: Shovkovy FP(04) [lectures].

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Send feedback and suggestions to bombelli at olemiss.edu – Modified 27 jun 2008