Optical manipulation of coherent phonons in superconducting YBa2Cu3O7-δ thin films

The coherent phonons of YBa2Cu3O7-delta are believed to be strongly coupled to its superconductivity. Controlling the phonons below its transition temperature, therefore, may serve as a promising scheme of the control of superconductivity. Here we demonstrate optical manipulation of the Ba-O and Cu-O vibrations in a thin-film YBa2Cu3O7-delta below its transition temperature using a pair of femtosecond laser pulses. The interpulse delay is tuned to integral and half-integral multiples of the oscillation period of a specific phonon mode (Ba-O or Cu-O vibration) to enhance and suppress its amplitude, respectively.