Thursday, July 16, 2009, 11:00 am — Small Seminar Room, Bldg. 510
Theories involving remarkably energetic spin fluctuations in cuprates are among the leading contenders for explaining high-temperature superconductivity. They are put to test by the inelastic neutron scattering (INS), where change in magnetic intensity upon a superconducting transition provides precise quantitative measure of the participating spin-interaction energy. However, absolute intensities of spin fluctuations measured in neutron scattering experiments vary widely and are usually much smaller than expected from fundamental sum rules. Here we report a detailed INS study of magnetic excitations in the one-dimensional cuprate relative Sr2CuO3, where the missing INS intensity can be unambiguously identified and associated with the covalent nature of the magnetic orbital. While excitation energies in Sr2CuO3 are well described by the exact theory for S=1/2 Heisenberg model, the magnetic neutron scattering intensity is modified dramatically by the strong 2p-3d Cu-O hybridization, showing that ionic picture with spins residing on atomic-like 3d orbitals is grossly inadequate.
Hosted by: Robert Konik
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