[In 1998, Argentinean physicist Juan] Maldacena made a conjecture in which he argued that there is a relationship between a strongly coupled quantum mechanical system and a gravitational system [that] is entirely classical Einsteinian gravity. So in fact, strongly coupled quantum mechanical systems that are charged are equivalent to a curved space-time with a black hole in it. We showed that if you just introduce some probe fermions and these probe fermions are coupled to the space-time in a particular way, that system looks identical to the normal [nonsuperconducting] state of high-temperature superconductors.
Others have used this mapping before. What we did that was new is that we used a particular interaction between the probe fermions and the black hole that is really irrelevant to the physics of the black hole but changes the physics at the boundary of the space-time [which is where the quantum mechanical theory lives]. No one suspected it.
With such a model, you can just forget about trying to figure out what the basic building blocks are, just go and solve this geometry problem and extrapolate it to what's going on at the surface of this geometry, and you'll see what the quantum mechanical system is doing.
A fascinating career arc.