Figure 1
Credit: Alan Stonebraker

Figure 1: (Top) Schematic phase diagram of cuprate superconductors as function of temperature T and doping level p. At half-filling, p=0, the materials are antiferromagnetic (AF) Mott insulators; superconductivity (SC) thus emerges from doping a Mott insulator. The doping range p<0.16 (p>0.16) is dubbed underdoped (overdoped), and the underdoped regime, p<0.16, is characterized by the pseudogap. Quantum oscillations have been detected at low T in large applied fields. (Bottom) Schematic evolution of the Fermi surface in a density-wave scenario. All panels show a quarter of the two-dimensional Brillouin zone, with occupied states shaded. On the far overdoped side, a large unreconstructed Fermi surface is seen. For smaller doping, but p>pc, the density-wave reconstruction induces electron pockets near (0,π), whereas those disappear for p<pc in favor of open orbits. (The existence of smaller pockets depends on microscopic details.)