Abstract
Measurements of spin excitations are essential for an understanding of spin-mediated pairing for superconductivity; and resonant inelastic X-ray scattering (RIXS) provides a considerable opportunity to probe high-energy spin excitations. However, whether RIXS correctly measures the collective spin excitations of doped superconducting cuprates remains under debate. Here we demonstrate distinct Raman- and fluorescence-like RIXS excitations of Bi1.5Pb0.6Sr1.54CaCu2O8+δ. Combining photon-energy and momentum dependent RIXS measurements with theoretical calculations using exact diagonalization provides conclusive evidence that the Raman-like RIXS excitations correspond to collective spin excitations, which are magnons in the undoped Mott insulators and evolve into paramagnons in doped superconducting compounds. In contrast, the fluorescence-like shifts are due primarily to the continuum of particle-hole excitations in the charge channel. Our results show that under the proper experimental conditions RIXS indeed can be used to probe paramagnons in doped high-Tc cuprate superconductors.
Highlights
Inelastic X-ray scattering is a powerful spectroscopic tool to probe charge fluctuations and lattice dynamics of materials[1,2]
The RIXS intensities for energy loss between 1 and 3 eV arise mostly from dd excitations in which the Cu 3dx2−y2 hole has been excited into previously filled 3d orbitals
It is generally agreed that, due to the large spin-orbit coupling for the core hole created in the intermediate state of the RIXS process, a 3d electron in the intensities shown in the color maps are after background subtraction
Summary
Inelastic X-ray scattering is a powerful spectroscopic tool to probe charge fluctuations and lattice dynamics of materials[1,2]. The Cu L3-edge RIXS, which does not require large sample volumes and can access relatively high energies, has been used to probe spin excitations in antiferromagnetic insulating[4,5,6,7,8], hole-doped[9,10,11,12,13,14,15], and electron-doped[16] cuprates The interpretation of these RIXS measurements in terms of a collective magnetic mode that evolves with doping from a coherent magnon in the undoped phase to a damped magnetic excitation—paramagnon—in the doped phase, is in dispute[9,10,11,12,13,14,15,17,18]. Predominantly arises from magnetic collective modes, but no results due to the continuum of particle-hole excitations are reported[15] To reconcile these seemingly contradictory findings and interpretations in doped superconducting cuprates, we performed comprehensive RIXS measurements on Bi1.5Pb0.6Sr1.54CaCu2O8+δ (Pb-Bi2212) together with theoretical analysis using small-cluster exact diagonalization (ED). Our results highlight the powerful role that X-ray polarization, incident photon energy, and momentum transfer associated with the RIXS process can have on identifying, characterizing, and disentangling low-energy RIXS excitations
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
