Change of carrier density at the pseudogap critical point of a cuprate superconductor

Understand

The pseudogap is a central puzzle of cuprate superconductors.

• Its connection to the Mott insulator at low doping $p$ remains ambiguous and its relation to the charge order that reconstructs the Fermi surface at intermediate $p$ is still unclear.
• Here we use measurements of the Hall coefficient in magnetic fields up to 88 T to show that Fermi-surface reconstruction by charge order in YBa$_2$Cu$_3$O$_y$ ends sharply at a critical doping $p = 0.16$, distinctly lower than the pseudogap critical point at $p^* = 0.19$.
• This shows that pseudogap and charge order are separate phenomena.