Pashkin, A. and Porer, M. and Beyer, M. and Kim, K.W. and Dubroka, A. and Bernhard, C. and Yao, X. and Dagan, Y. and Hackl, R. and Erb, A. and Demsar, J. and Huber, Rupert and Leitenstorfer, A.
Femtosecond Response of Quasiparticles and Phonons in Superconducting YBa2Cu3O7-δ Studied by Wideband Terahertz Spectroscopy.
Physical Review Letters (PRL) 105 (6), 067001.
We measure the anisotropic midinfrared response of electrons and phonons in bulk YBa2Cu3O7-δ after femtosecond photoexcitation. A line shape analysis of specific lattice modes reveals their transient occupation and coupling to the superconducting condensate. The apex oxygen vibration is strongly excited within 150 fs, demonstrating that the lattice absorbs a major portion of the pump energy before the quasiparticles are thermalized. Our results attest to substantial electron-phonon scattering and introduce a powerful concept probing electron-lattice interactions in a variety of complex materials.