Magnetic-Field Tuning of Light-Induced Superconductivity in Striped La_2−xBa_xCuO₄

Optical excitation of stripe-ordered La2−xBaxCuO4 has been shown to transiently enhance superconducting tunneling between the CuO2 planes. This effect was revealed by a blue-shift, or by the appearance of a Josephson Plasma Resonance in the terahertz-frequency optical properties. Here, we show that this photo-induced state can be strengthened by the application of high external magnetic fields oriented along the c-axis. For a 7-Tesla field, we observe up to a ten-fold enhancement in the transient interlayer phase correlation length, accompanied by a two-fold increase in the relaxation time of the photo-induced state. These observations are highly surprising, since static magnetic fields suppress interlayer Josephson tunneling and stabilize stripe order at equilibrium. We interpret our data as an indication that optically-enhanced interlayer coupling in La2−xBaxCuO4 does not originate from a strengthening of the equilibrium superconductor that competes with stripes, as previously hypothesized. Rather, these results suggest that the photo-induced state may emerge from activated tunneling between optically-excited pair-density-waves in adjacent planes