Light reveals competing pseudogap in doped cuprate superconductors

Photoexcitation can transform the electronic spectrum of an optimally doped bismuth-based cuprate from a particle–hole-symmetric superconducting state into an asymmetric pseudogap-like state, according to a time- and angle-resolved photoemission study reported in Nature Physics. The researchers directly examined the near-antinodal region of the Fermi surface and found that the change occurred when a sufficiently intense laser pulse disrupted superconductivity. The altered state emerged at electronic temperatures well below the material’s equilibrium superconducting critical temperature, indicating that it was not simply a conventional thermal response.

The experiment focuses on the unusual electronic landscape of high-temperature cuprate superconductors, materials in which superconductivity coexists and competes with other quantum phases, including a pseudogap and non-Fermi-liquid transport. The study used time- and angle-resolved photoemission to measure how the density of electronic states evolved after light excitation and subsequently recovered. By resolving the near-antinodal momentum region, the team could distinguish a symmetric, superconducting-like spectrum from an asymmetric state associated with the pseudogap. Before excitation, the low-energy spectral response was consistent with superconductivity; after a strong enough pulse, it instead displayed the asymmetric pseudogap-like form.

At intermediate times or intermediate excitation fluences, the researchers observed spectra containing both pseudogap and superconducting features. This allowed them to follow the progression between the two states rather than treating the response as an instantaneous switch. The light-induced asymmetric state persisted while the electronic system was still very cold, and the spectral recovery coincided with the restoration of a particle–hole-symmetric density of states. When superconductivity returned fully, the pseudogap signature was suppressed. The measurements therefore connect the disappearance and reappearance of one electronic state with the emergence and disappearance of the other during the material’s transient response.

The authors also tested whether the altered spectrum could be explained solely by heating. Their analysis indicated that the light-induced pseudogap was non-thermal, supported in part by tracking the transient electronic temperature through Fermi-surface mapping. The distinction is important because the observed asymmetric spectrum appeared at electronic temperatures well below the equilibrium critical temperature, away from the regime in which thermal effects alone would explain the pseudogap-like response. The study’s figure captions identify the tracking of transient electronic temperature and the non-thermal character of the light-induced state as separate elements of the analysis.

These results challenge the view that superconductivity in cuprates emerges simply from establishing phase coherence within an underlying pseudogap. Instead, the measurements support a dynamic competition between the superconducting and pseudogap states. The authors interpret the findings as evidence that the low-temperature ground state of cuprates reflects an interplay between these phases. Because the study targets a particular near-antinodal region of optimally doped bismuth-based cuprates, however, it does not establish how broadly the effect extends across different materials, doping levels or parts of the Fermi surface. The evidence concerns a transient light-driven state in a specific class of cuprate rather than the full equilibrium phase diagram.

Subject of Research: Experimental investigation of light-driven competition between superconductivity and the pseudogap in optimally doped bismuth-based cuprates

Article Title: Light-induced asymmetric pseudogap below the critical temperature in cuprates

Article References: Armanno, D., Gingras, O., Goto, F., Parent, J. M., Longa, A., Jabed, A., Frimpong, B., Zhong, R. D., Schneeloch, J., Gu, G. D., Jargot, G., Ibrahim, H., Légaré, F., Siwick, B. J., Gauthier, N., Georges, A., Millis, A. J., & Boschini, F. (2026). Light-induced asymmetric pseudogap below the critical temperature in cuprates. Nature Physics. https://doi.org/10.1038/s41567-026-03446-6

Image Credits: AI Generated

DOI: 10.1038/s41567-026-03446-6

Keywords: cuprate superconductors, pseudogap, superconductivity, photoemission, quantum phases, bismuth compounds, electron spectroscopy, non-thermal state, Fermi surface, Light-induced, asymmetric, below