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ishsiokaphysrevb.107.1843022023
Journal article

Selective coupling of coherent optical phonons in YBa2Cu3O7−δ with electronic transitions

DOKPE

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  • 2023
Published in:
  • Physical Review B. - American Physical Society (APS). - 2023, vol. 107, no. 18, p. 184302(1-16)
Infrared spectroscopy
Cuprate high Tc superconductor
Electron-phonon coupling
Optical phonons
Photoexcitation
Reflectivity
Transient absorption spectroscopy
English We investigate coherent lattice dynamics in optimally doped YBa2Cu3O7−δ driven by ultrashort (∼12 fs) near infrared and near-ultraviolet pulses. Transient reflectivity experiments, performed at room temperature and under moderate (<0.1 mJ/cm2) excitation fluence, reveal Ag-symmetry phonon modes related to the O(2,3) bending in the CuO2 planes and to the apical O(4) stretching at frequencies between 10 and 15 THz, in addition to the previously reported Ba and Cu(2) vibrations at 3.5 and 4.5 THz. The relative coherent phonon amplitudes are in stark contrast to the relative phonon intensities in the spontaneous Raman scattering spectrum excited at the same wavelength. This contrast indicates mode-dependent contributions of the Raman and non-Raman mechanisms to the coherent phonon generation. We show that the particularly intense coherent Cu(2) phonon, together with its initial phase, supports its generation predominately via a displacive mechanism, possibly involving the charge transfer within the CuO2 planes. The small amplitude of the coherent out-of-phase O(2,3) bending mode at 10 THz also suggests the involvement of non-Raman generation mechanism. The generation of the other coherent phonons can in principle be explained within the framework of Raman mechanism. When the pump light has the polarization component perpendicular to the CuO2 plane, the coherent O(4) mode at 15 THz is strongly enhanced compared to the in-plane excitation, corresponding to the large polarizability component associated with the hopping between the apical and the chain oxygens, O(4) and O(1).
Faculty
Faculté des sciences et de médecine
Department
Département de Physique
Language
  • English
Classification
Physics
License
Rights reserved
Open access status
green
Identifiers
Persistent URL
https://folia.unifr.ch/unifr/documents/333323
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