Resonant Inelastic X-Ray Scattering Study of Electron-Exciton Coupling in High- Tc Cuprates

F. Barantani, M. K. Tran, I. Madan, I. Kapon, N. Bachar, T. C. Asmara, E. Paris, Y. Tseng, W. Zhang, Y. Hu, E. Giannini, G. Gu, T. P. Devereaux, C. Berthod, F. Carbone, T. Schmitt, D. Van Der Marel

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Explaining the mechanism of superconductivity in the high-Tc cuprates requires an understanding of what causes electrons to form Cooper pairs. Pairing can be mediated by phonons, the screened Coulomb force, spin or charge fluctuations, excitons, or by a combination of these. An excitonic pairing mechanism has been postulated, but experimental evidence for coupling between conduction electrons and excitons in the cuprates is sporadic. Here we use resonant inelastic x-ray scattering to monitor the temperature dependence of the d_d exciton spectrum of Bi2Sr2CaCu2O8-x crystals with different charge carrier concentrations. We observe a significant change of the d_d exciton spectra when the materials pass from the normal state into the superconductor state. Our observations show that the d_d excitons start to shift up (down) in the overdoped (underdoped) sample when the material enters the superconducting phase. We attribute the superconductivity-induced effect and its sign reversal from underdoped to overdoped to the exchange coupling of the site of the d_d exciton to the surrounding copper spins.

Original languageEnglish
Article number021068
Number of pages14
JournalPhysical Review X
Issue number2
StatePublished - 29 Jun 2022

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)


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