Symmetry-protected electronic metastability in an optically driven cuprate ladder

TL;DR

This study demonstrates how optical excitation can induce long-lived, symmetry-protected electronic metastable states in a cuprate ladder, revealing a new method to control nonequilibrium phases in quantum materials.

Contribution

The paper uncovers a mechanism for creating long-lived metastable states via symmetry-protected charge transfer, enabled by ultrafast optical dressing in a cuprate ladder.

Findings

Optical excitation transfers holes into ladders, creating metastability.

Symmetry protection suppresses relaxation back to ground state.

Ultrafast charge redistribution is driven by symmetry-forbidden hopping pathways.

Abstract

Optically excited quantum materials exhibit nonequilibrium states with remarkable emergent properties, but these phenomena are usually transient, decaying on picosecond timescales and limiting practical applications. Advancing the design and control of nonequilibrium phases requires the development of targeted strategies to achieve long-lived, metastable phases. Here, we report the discovery of symmetry-protected electronic metastability in the model cuprate ladder Sr$_{14}$Cu$_{24}$O$_{41}$. Using femtosecond resonant x-ray scattering and spectroscopy, we show that this metastability is driven by a transfer of holes from chain-like charge reservoirs into the ladders. This ultrafast charge redistribution arises from the optical dressing and activation of a hopping pathway that is forbidden by symmetry at equilibrium. Relaxation back to the ground state is hence suppressed after the pump coherence dissipates. Our 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.