High-Temperature Superconductivity is something I worked on at Stanford back in 1973-75. The world has changed. Now “high-temperature” means “above the boiling point of liquid Nitrogen” (77^oK/-321^oF). Back then it meant “above the boiling point of liquid Hydrogen” (20^oK/-423^oF), and it was still an unattained goal. We had to use liquid Helium. Still, some things remain the same:

1. Dimensionality matters. Back then I was working with thin films, thin enough to act in some ways like two-dimensional objects. This is still important.
2. The Ginzburg-Landau macroscopic theory seems to still work. The more detailed BCS Theory goes beyond G-L to a give a microscopic description of superconductivity and is very successful at liquid Helium temperatures. However, it appears to be in trouble at higher temperatures.