A copper crystal is squeezed in diamond anvil cells. As pressure mounts, a battle unfolds inside the material between two states: one prepares electrons for superconductivity, the other hinders their pairing. Scientists tracked this struggle using ultrashort laser pulses.
Spectroscopy revealed that the temperature at which the pseudogap appears (a state with partially blocked electrons) rises with pressure. But the pseudogap's own energy gap narrows. Superconductivity, however, follows its own course: its critical temperature and gap first increase, peak, and then drop. The two orders are not synchronized.
By 37 GPa, superconductivity completely disappears, leaving an insulating state. This scenario indicates that the pseudogap is not a "precursor" to superconductivity but an independent competitor. This is an important step toward understanding high-temperature superconductivity.
A pressure of 37 GPa is roughly 370,000 times atmospheric pressure. Such pressure exists inside Earth at a depth of about 1000 km.
In Arthur C. Clarke's novel "Childhood's End," aliens use superconductors for levitation, but there is no hint of a pseudogap.