Figure 2: (a) Phase diagram of the cuprates. At low carrier doping, one has an antiferromagnetic insulator, at higher dopings, a $d$-wave superconductor. $T^{*}$ is the temperature below which an energy gap appears, marking the pseudogap phase. (b) ARPES intensity at the Fermi energy for a doping of $0.1$, showing a “Fermi arc.” The red curve encloses an area equal to the oscillation frequency observed in the Hall resistance of underdoped $\text{YBCO}$. (c) ARPES intensity at the Fermi energy for a doping of $0.25$, showing a large Fermi surface instead. The red curve is the prediction of paramagnetic band theory, and its area matches a subsequent oscillation study on overdoped Tl2201.