Light-Driven Switch for Metastable Charge Trapping in a Cuprate Ladder

Precision control of charge carrier density is a key capability that underpins modern technology. It also plays a central role in strongly correlated materials, where the carrier density provides a powerful handle on emergent phenomena, for example enhancing superconducting critical temperatures by orders of magnitude and tipping the balance between competing ordered phases. However, conventional approaches to realizing this, such as chemical substitution, are slow, introduce deleterious structural disorder, and are furthermore a static and irreversible process. Here, we demonstrate a modality to dynamically control the carrier density, by transiently manipulating atomistic pathways for charge tunnelling in the Sr_14-xCa_xCu₂₄O₄₁ family of superconducting ladders. We achieve this using intense, ultrashort pulses of light that break the approximate fourfold symmetry of the CuO₄ plaquettes, activating a transient tunnelling pathway between the ladder sublattice and the charge reservoir layer. This results in a transfer of holes into the ladder, where they are subsequently trapped for several nanoseconds, manifesting as a characteristic reshaping of the time-resolved X-ray absorption spectra. Furthermore, employing time-resolved resonant X-ray scattering, we find that the trapped holes suppress the charge order and short-range spin correlations, even as the ladder approaches the carrier density at which superconductivity onsets. Our work demonstrates a new strategy towards achieving long-lived light-induced phenomena and paves the way towards functionalizing them.