Mode-Selective Coupling of Coherent Phonons to the Bi2212 Electronic Band Structure

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Cuprate superconductors exhibit complex electronic properties influenced by low-energy optical phonons.
• Understanding the coupling between electrons and phonons is key to elucidating superconductivity mechanisms.

Purpose of the Study:

• To investigate coherent phonon dynamics in Bi2Sr2Ca0.92Y0.08Cu2O8+δ using time- and angle-resolved photoemission spectroscopy (Ta-ARPES).
• To identify the specific phonon modes interacting with the electronic band structure and their origin.

Main Methods:

• Time- and angle-resolved photoemission spectroscopy (Ta-ARPES) was employed to probe electronic band structure modulations.
• Theoretical calculations were performed to identify the symmetry and origin of the observed phonon modes.

Main Results:

• Sub-millielectronvolt (meV) modulations in the electronic band structure were observed at 3.94 THz and 5.59 THz.
• The dominant 3.94 THz phonon mode showed a weak increase in oscillation amplitude with momentum away from the node.
• Observed modes were identified as CuO2-derived A1g phonons, distinct from Bi- and Sr-derived modes typically seen in Raman spectra.

Conclusions:

• The study highlights mode selectivity in phonon-electron coupling, with CuO2-derived phonons being dominant for near-Fermi-level electrons.
• These findings underscore the importance of CuO2-plane phonons in dictating the thermodynamic properties of cuprate superconductors.