A key piece of the evidence for strong correlations is recent inelastic neutron scattering experiments reported in this Nature Physics paper.
They show that even in the superconducting materials [which are doped from parent Antiferromagnetic compounds] there are sizeable fluctuating magnetic moments. The figure below shows the dynamical spin susceptibility versus energy. For both superconducting and antiferromagnetic materials the susceptibility is essentially the same for energies above 100 meV.
Furthermore, a weak coupling RPA treatment [which is invoked to explain the superconductivity] cannot capture the magnitude of these spin fluctuations. In contrast, a DMFT treatment from Park, Haule, and Kotliar is consistent with the experimental data, highlighting the role of strong correlations and Hund's rule coupling.
except for this,
ReplyDeleteElectronic correlations in the iron pnictides
M. M. Qazilbash, J. J. Hamlin, R. E. Baumbach, Lijun Zhang, D. J. Singh, M. B. Maple, D. N. Basov
Journal reference: Nature Physics 5, 647 (2009)
Cite as: arXiv:0909.0312
and this,
arXiv:0905.2633 [pdf, ps, other]
Evidence for weak electronic correlations in Fe-pnictides
W. L. Yang, P. O. Velasco, J. D. Denlinger, A. P. Sorini, C-C. Chen, B. Moritz, W.-S. Lee, F. Vernay, B. Delley, J.-H. Chu, J. G. Analytis, I. R. Fisher, Z. A. Ren, J. Yang, W. Lu, Z. X. Zhao, J. van den Brink, Z. Hussain, Z.-X. Shen, T. P. Devereaux
Phys. Rev. B 80, 014508 (2009
The main point being that probably in the 11-compounds they have stronger correlations than in like the 1111 compounds, and we cant always view the iron-SCs as all the same...
ReplyDeleteSince Abrahams and Si and others were very early in suggestions to treat these materials as strongly correlated there possibly maybe could be self interest in promoting that perspective.