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Anisotropic softening of magnetic excitations along the nodal direction in superconducting cuprates

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Guarise M., Dalla Piazza B., Berger H., Giannini E., Schmitt T., Ronnow H. M., Sawatzky G. A., van den Brink J., Altenfeld D., Eremin I., Grioni M.,
Project Quantum Magnetism - Spinons, Skyrmions and Dipoles
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Original article (peer-reviewed)

Journal NATURE COMMUNICATIONS
Volume (Issue) 5
Page(s) 6760
Title of proceedings NATURE COMMUNICATIONS
DOI 10.1038/ncomms6760

Open Access

URL https://infoscience.epfl.ch/record/205534?ln=en
Type of Open Access Repository (Green Open Access)

Abstract

The high-T-c cuprate superconductors are close to antiferromagnetic order. Recent measurements of magnetic excitations have reported an intriguing similarity to the spin wavesmagnons- of the antiferromagnetic insulating parent compounds, suggesting that magnons may survive in damped, broadened form throughout the phase diagram. Here we show by resonant inelastic X-ray scattering on Bi2Sr2CaCu2O8+delta (Bi-2212) that the analogy with spin waves is only partial. The magnon-like features collapse along the nodal direction in momentum space and exhibit a photon energy dependence markedly different from the Mott-insulating case. These observations can be naturally described by the continuum of charge and spin excitations of correlated electrons. The persistence of damped magnons could favour scenarios for superconductivity built from quasiparticles coupled to spin fluctuations. However, excitation spectra composed of particle-hole excitations suggest that superconductivity emerges from a coherent treatment of electronic spin and charge in the form of quasiparticles with very strong magnetic correlations.
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