A new study has revealed the coexistence of persistent Fermi pockets and robust electron pairing in the CuO₂ layers of lightly doped cuprate superconductors. This finding is crucial for understanding the nature of the pseudogap phase and the origin of high-temperature superconductivity in these materials. The persistence of these features across the pseudogap-superconductor transition suggests that the electronic foundations of the superconducting state are already present in the pseudogap phase, a regime that has eluded a complete description for decades.

Cuprates are known for their ability to conduct electricity without resistance at relatively high temperatures, but the exact mechanism behind this superconductivity remains one of the biggest mysteries in condensed matter physics. The pseudogap phase, which appears at temperatures above the superconducting transition temperature, is characterized by a partial suppression of the electronic density of states at the Fermi surface. The observation of well-defined Fermi pockets, rather than a completely open Fermi surface, challenges some of the prevailing theories about the pseudogap and points to a more complex reorganization of electronic states.

This discovery was achieved using advanced spectroscopic techniques that allowed probing the electronic structure of the materials with unprecedented resolution. The obtained data provide direct evidence that electron pairing, a prerequisite for superconductivity, is already active in the pseudogap phase, implying that the pseudogap could be a direct precursor to the superconducting state. Understanding the relationship between the pseudogap, Fermi pockets, and electron pairing is fundamental for developing a unified theory of high-temperature superconductivity and, potentially, for designing new superconducting materials at even higher temperatures.