Chandra Varma is a theoretical physicist at University of California, Riverside. A couple years ago, he gave a talk at my institution purporting to explain superconductivity in the cuprates. It all sounded so great and convincing, and I want to know what the status is with that.
Here (link) (arxiv version link) is a 2006 paper explaining his theory in detail, and here (link) is a more recent one. Supposedly, there is a spontaneous breaking of time-reversal symmetry, resulting in microscopic currents with long-range order, running in loops between the copper and oxygen atoms. These currents can function as the glue for electron-electron pairing. These currents, which are very hard to detect, have actually been seen by spin-polarized ARPES and by spin-polarized neutron diffraction. Here (link) and here (link) is the spin-polarized neutron diffraction study, and Here (link) is a more recent 2010 neutron-scattering experiment confirming the same results, published in Nature. Here (link) is a report of him discussing his theory with other experts in superconductivity theory.
So, as far as I can tell, this is a simple, elegant, experimentally-proven theory explaining cuprate superconductivity. The theory and supporting experiments are at least five years old. But everyone still says that cuprate superconductivity is a mystery. What's the deal? Is there a problem or controversy in this theory? Does the theory explain only a small part of the mystery of superconductivity? Am I misunderstanding something?
(I am a condensed-matter physicist but not a superconductivity specialist.)