The intricate phase diagram of high-temperature cuprate superconductors is still subject of many investigations and debates. One of the many unanswered questions is the origin of the interplay between the 2D Charge Density Wave (CDW), 3D-CDW, and high-temperature superconductivity (SC). One important mediator of this interplay is believed to be the electron-phonon interaction.

Our previous results using high-resolution inelastic X-ray scattering (IXS) on YBa2Cu3O6+x have revealed a strong renormalization of low-energy phonons across Tc, which was interpreted as a the hybridization between phonons and collective CDW excitation. [1] Interestingly , this effect is the strongest at q3DCDW, even when The 3D-CDW order was not formed in the experimental conditions.

This poster presents our latest results on the IXS study of the competing order of YBa2Cu3O6+x, using uniaxial strain, and temperature as the external parameters. Uniaxial strain allowed to investigate this low-energy phonon renormalization in an extended portion of the phase diagram, as it is a very efficient tuning parameter of the interplay between the CDW and the superconductivity, and allows us to reach the 3D CDW phase. [2,3] Our results unequivocally show that this renormalization process is not only the strongest at q3DCDW, but is also tightly bound to the SC state, as it is significantly enhanced in the SC phase independently of how close the system is from the 3DCDW. This confirms that hybridization between low-energy phonons and the dispersive excitations of the 3D-CDW under the effect of the superconductivity, shedding new light on the interplay between those electronic orders.

References:
[1] S.M. Souliou, et al., Communication Physics | (2025)8:362
[2] H.-H. Kim et al., Science 362, 1040–1044 (2018)
[3] I. Vinograd et al., Nature Communications | (2024)15:3277