Abstract
We report on a photoinduced transient state of O in which transport perpendicular to the Cu-O planes becomes highly coherent. This effect is achieved by excitation with mid-infrared optical pulses, tuned to the resonant frequency of apical oxygen vibrations, which modulate both lattice and electronic properties. Below the superconducting transition temperature , the equilibrium signatures of superconducting interlayer coupling are enhanced. Most strikingly, the optical excitation induces a new reflectivity edge at higher frequency than the equilibrium Josephson plasma resonance, with a concomitant enhancement of the low-frequency imaginary conductivity . Above , the incoherent equilibrium conductivity becomes highly coherent, with the appearance of a reflectivity edge and a positive that increases with decreasing frequency. These features are observed up to room temperature in O and O The data above can be fitted by hypothesizing that the light establishes a transient superconducting state over only a fraction of the solid, with a lifetime of a few picoseconds. Non-superconducting transport could also explain these observations, although one would have to assume transient carrier mobilities near 10 cm/V sec at 100 K, with a density of charge carriers similar to the below- superfluid density. Our results are indicative of highly unconventional nonequilibrium physics and open new prospects for optical control of complex solids.
4 More- Received 18 March 2014
- Revised 25 April 2014
DOI:https://doi.org/10.1103/PhysRevB.89.184516
©2014 American Physical Society