A quantum tug-of-war limits cuprate superconductivity
Cuprate experiments show the pseudogap competes with superconductivity rather than helping it form.
For more than three decades, cuprates have been the central puzzle in high-temperature superconductivity. They can carry current without resistance at temperatures far above conventional superconductors, but they also host a strange intervening regime called the pseudogap, where electrons partially organize as if a gap is opening long before the material actually becomes superconducting. Whether that pseudogap helps superconductivity get started or gets in its way has been one of the field’s most persistent arguments.
A collaboration between the Flatiron Institute and INRS has now come down firmly on the side of rivalry. The team used laser pulses and computer simulations to show that superconductivity and the pseudogap state compete rather than cooperate in cuprate materials, according to work published October 20 in Nature Physics. The experiment was designed as a direct test of coexistence: rather than watching the two states in equilibrium, the researchers drove the system out of balance and tracked how each responded.
That approach reveals a hidden rivalry between superconductivity and the pseudogap in cuprates, showing they compete for dominance rather than work together, as described by the INRS-led team. In that picture the pseudogap is not a precursor that pre-forms the pairs needed for superconductivity, but a distinct order that vies for the same electrons. When one gets stronger, the other weakens.
The tug-of-war framing matters because the precursor hypothesis has long offered an optimistic route to higher transition temperatures: if the pseudogap were already doing part of the work, stabilizing it might help superconductivity emerge at warmer conditions. A direct competition points the other way. If the two phases are fighting over spectral weight and coherence, then the pseudogap is a limit on superconductivity in cuprates rather than a launchpad for it.
The combination of ultrafast laser excitation and simulation was key to seeing that competition in real time. By perturbing the material and simulating the quantum dynamics that follow, the team could watch the two orders push against each other instead of inferring their relationship from static snapshots of the phase diagram. That out-of-equilibrium view makes the trade-off explicit in a way that steady-state measurements have struggled to resolve.
If competition is the rule, the path to pushing cuprates toward higher temperatures looks less like nurturing the pseudogap and more like finding ways to suppress it without also damaging superconductivity itself. It reframes the engineering problem from cooperation to control — understanding what tips the balance between two quantum states that want the same ground, and learning how to make superconductivity win.