Abstract

Coherent optical driving in quantum solids is emerging as a research frontier, with many reports of interesting non-equilibrium quantum phases and transient photo-induced functional phenomena such as ferroelectricity magnetism and superconductivity. In high-temperature cuprate superconductors, coherent driving of certain phonon modes has resulted in a transient state with superconductinglike optical properties, observed far above their transition temperature T_c and throughout the pseudogap phase . However, questions remain on the microscopic nature of this transient state and how to distinguish it from a non-superconducting state with enhanced carrier mobility. For example, it is not known whether cuprates driven in this fashion exhibit Meissner diamagnetism. Here we examine the timedependent magnetic field surrounding an optically driven YBa₂Cu₃O_6.48 crystal by measuring Faraday rotation in a magneto-optic material placed in the vicinity of the sample. For a constant applied magnetic field and under the same driving conditions that result in superconducting-like optical properties , a transient diamagnetic response was observed. This response is comparable in size with that expected in an equilibrium type II superconductor of similar shape and size with a volume susceptibility χ_v of order −0.3. This value is incompatible with a photo-induced increase in mobility without superconductivity. Rather, it underscores the notion of a pseudogap phase in which incipient superconducting correlations are enhanced or synchronized by the drive.