Abstract
Cuprate superconductors host a multitude of low-energy optical phonons. Using time- and angle-resolved photoemission spectroscopy, we study coherent phonons in . Sub-meV modulations of the electronic band structure are observed at frequencies of and . For the dominant mode at 3.94 THz, the amplitude of the band energy oscillation weakly increases as a function of momentum away from the node. Theoretical calculations allow identifying the observed modes as -derived phonons. The Bi- and Sr-derived modes which dominate Raman spectra in the relevant frequency range are absent in our measurements. This highlights the mode selectivity for phonons coupled to the near-Fermi-level electrons, which originate from planes and dictate thermodynamic properties.
- Received 26 September 2017
- Revised 17 November 2018
DOI:https://doi.org/10.1103/PhysRevLett.122.176403
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