Most materials are either metals or insulators. When they
are metals, their electronic properties are usually described by Landau's Fermi
liquid theory. That is, they behave more or less like a free Fermi gas, with a
few modifications due to electron-electron interactions.
However, there exist a few metallic materials whose
phenomenology does not fit within Fermi liquid theory. These are quasi-2D
metals on the verge of becoming insulators, and they happen to become
superconducting at low temperature, by a mechanism different than BCS
superconductivity. The physics of these materials calls for a new strongly
coupled phase of interacting electrons, yet to be understood.
I will describe recent progress in describing such a
phase using the holographic duality.