I thought it might be fun to survey people for examples of condensed matter and materials physics as they show up in science fiction (and/or comics, which are fantasy more than hard SF). I don't mean examples where fiction gets science badly wrong or some magic rock acts as a macguffin (Infinity Stones, Sankara stones) - I mean cases where materials and their properties are thought-provoking.
A couple of my favorites:
- scrith, the bizarre material used to construct the Ringworld. It's some exotic material that has 40% opacity to neutrinos without being insanely dense like degenerate matter.
- From the same author, shadow square wire, which is an absurdly strong material that also doubles as a high temperature superconductor. (Science goof in there: Niven says that this material is also a perfect (!) thermal conductor. That's incompatible with superconductivity, though - the energy gap that gives you the superconductivity suppresses the electronic contribution to thermal conduction. Ahh well.)
- Even better, from the same author, the General Products Hull, a giant single-molecule structure that is transparent in the visible, opaque to all other wavelengths, and where the strength of the atomic bonds is greatly enhanced by a fusion power source.
- Vibranium, the light, strong metal that somehow can dissipate kinetic energy very efficiently. (Like many materials in SF, it has whatever properties it needs to for the sake of the plot. Hard to reconcile the dissipative properties with Captain America's ability to bounce his shield off objects with apparently perfect restitution.)
- Old school: cavorite, the H. G. Wells wonder material that blocks the gravitational interaction.