Revealing the Coulomb interaction strength in a cuprate superconductor

S.-L. Yang; J. A. Sobota; Y. He; Y. Wang; D. Leuenberger; H. Soifer; M. Hashimoto; D. H. Lu; H. Eisaki; B. Moritz; T. P. Devereaux; P. S. Kirchmann; Z.-X. Shen

doi:10.1103/PhysRevB.96.245112

Revealing the Coulomb interaction strength in a cuprate superconductor

S.-L. Yang, J. A. Sobota, Y. He, Y. Wang, D. Leuenberger, H. Soifer, M. Hashimoto, D. H. Lu, H. Eisaki, B. Moritz, T. P. Devereaux, P. S. Kirchmann, Z.-X. Shen

DOI 10.1103/PhysRevB.96.245112 · Physical Review B

T1

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Abstract

We study optimally doped Bi2Sr2Ca0.92Y0.08Cu2O8+δ (Bi2212) using angle-resolved two-photon photoemission spectroscopy. Three spectral features are resolved near 1.5, 2.7, and 3.6 eV above the Fermi level. By tuning the photon energy, we determine that the 2.7-eV feature arises predominantly from unoccupied states. The 1.5- and 3.6-eV features reflect unoccupied states whose spectral intensities are strongly modulated by the corresponding occupied states. These unoccupied states are consistent with the prediction from a cluster perturbation theory based on the single-band Hubbard model. Through this comparison, a Coulomb interaction strength U of 2.7 eV is extracted. Our study complements equilibrium photoemission spectroscopy and provides a direct spectroscopic measurement of the unoccupied states in cuprates. The determined Coulomb U indicates that the charge-transfer gap of optimally doped Bi2212 is 1.1 eV.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Bi2Sr2Ca0.92Y0.08Cu2O8+δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	96	Pressure not reported	unknown