Interpretation of light-induced superconducting-like responses in cuprates

Determine whether transient low-frequency electrodynamics and diamagnetic responses induced by mid-infrared excitation in underdoped YBa₂Cu₃O₆₊ₓ and related cuprates arise from enhanced interlayer superconducting coherence or from nonequilibrium effects such as photoexcited quasiparticles and coexisting changes in c-axis and in-plane electrodynamics.

Background

The paper reviews experiments in which mid-infrared excitation of infrared-active phonons in underdoped YBa₂Cu₃O₆₊ₓ reorganizes lattice coordinates and produces transient low-frequency electrodynamic signatures resembling enhanced interlayer coherence. A diamagnetic response has also been reported under related conditions, raising the possibility of light-induced superconducting correlations or transient superconductivity.

However, the review notes that other measurements emphasize photoexcited quasiparticles and report the coexistence of a c-axis reflectivity edge with enhanced in-plane scattering. These competing observations leave unresolved whether the observed signatures reflect genuine enhancement of superconducting coherence or alternative nonequilibrium optical and transport processes.

References

The interpretation of these responses remains debated up to now, for other measurements in cuprates have emphasized photoexcited quasiparticles and the coexistence of a $c$-axis reflectivity edge with enhanced in-plane scattering.

— Probing and Manipulating Quantum Materials with Strong-field Terahertz and Mid-infrared Radiation  (2610.11126 - Li et al., 8 Oct 2026) in Section 5, subsection “Resonant collective-mode control of ordered states,” paragraph “Indirect control through auxiliary-mode coupling”