title: Measurement of magnetic excitations in the two-dimensional antiferromagnetic Sr₂CuO₂Cl₂ insulator using resonant x-ray scattering: evidence for extended interactions.
abstract: We measured the momentum dependence of magnetic excitations in the model spin-1/2 2D antiferromagnetic insulator Sr2CuO2Cl2 (SCOC). We identify a single-spin-wave feature and a multimagnon continuum, with different polarization dependences. The spin waves display a large (70 meV) dispersion between the zone-boundary points (π, 0) and (π/2, π/2). Employing an extended t-t'-t''-U one-band Hubbard model, we find significant electronic hopping beyond nearest-neighbor Cu ions, indicative of extended magnetic interactions. The spectral line shape at (π, 0) indicates sizable quantum effects in SCOC and probably more generally in the cuprates.
authors.affiliation: Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne, CH-1015, Switzerland.
authors.forename: M
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authors.lastname: Guarise
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authors.lastname: Dalla Piazza
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authors.lastname: Moretti Sala
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authors.lastname: Ghiringhelli
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authors.lastname: Braicovich
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authors.lastname: Hancock
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authors.lastname: van der Marel
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authors.lastname: van den Brink
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authors.lastname: Lin
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authors.lastname: Xu
authors.forename: H M
authors.initials: HM
authors.lastname: Rønnow
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authors.lastname: Grioni