Electronic metastability in a one-dimensional cuprate

Optically excited quantum materials exhibit nonequilibrium states with remarkable emergent properties, but these phenomena are usually short-lived, decaying on picosecond timescales and limiting practical applications. In rare instances, photoexcited solids become trapped in metastable states due to material-specific relaxation bottlenecks. Advancing the design and control of nonequilibrium metastable phases requires a microscopic understanding of their underlying mechanisms and the development of targeted excitation strategies. Here, we report the observation of photo-induced metastability in a prototypical one-dimensional cuprate ladder Sr₁₄Cu₂₄O₄₁. Using femtosecond resonant x-ray scattering and spectroscopy, we show that this metastability involves a transfer of holes from chain-like charge reservoirs into the ladders. The nonequilibrium charge redistribution originates from the optical dressing and activation of a hopping pathway that is forbidden by symmetry at equilibrium. Relaxation back to the ground state is then suppressed after the pump coherence dissipates. These findings highlight how dressing materials with electromagnetic fields can dynamically activate terms in the electronic Hamiltonian, and provide a rational design strategy for nonequilibrium phases of matter.