Optically Induced Superconductivity in Striped $\mathrm{La_{2−x}Ba_xCuO_4}$ by Polarization-Selective Excitation in the Near Infrared

We show that superconducting interlayer coupling, which coexists with and is depressed by stripe order in $La_{1.885}Ba_{0.115}CuO_4$, can be enhanced by excitation with near-infrared laser pulses. For temperatures lower than T$_c$ =13 K, we observe a blue shift of the equilibrium Josephson plasma resonance, detected by terahertz-frequency reflectivity measurements. Key to this measurement is the ability to probe the optical properties at frequencies as low as 150 GHz, detecting the weak interlayer coupling strengths. For T >T$_c$ a similar plasma resonance, absent at equilibrium, is induced up to the spin-ordering temperature TS$_O$ $\backsimeq$ 40 K. These effects are reminiscent but qualitatively different from the light-induced superconductivity observed by resonant phonon excitation in $La_{1.675}Eu_{0.2}Sr_{0.125}CuO_{6.5}$. Importantly, enhancement of the below-T$_c$ interlayer coupling and its appearance above T$_c$ are preferentially achievedwhen the near-infrared pump light is polarized perpendicular to the superconducting planes, likely due to more effective melting of stripe order and the less effective excitation of quasiparticles from the Cooper pair condensate when compared to in-plane excitation