Publication Detail / Abstract

We show that superconducting interlayer coupling, which coexists with and is depressed by stripe order in La_1.885Ba_0.115CuO₄, 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 T_SO ≃ 40 K. These effects are reminiscent but qualitatively different from the light-induced superconductivity observed by resonant phonon excitation in La_1.675Eu_0.2Sr_0.125CuO_6.5. Importantly, enhancement of the below-T_c interlayer coupling and its appearance above T_c are preferentially achieved when 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.