MAGNETIC NEUTRON-SCATTERING FROM 2-DIMENSIONAL LATTICE ELECTRONS - THE CASE OF LA2-XSRXCUO4

It is found that the one-band Hubbard model, in the weak- to intermediate-coupling regime, can account qualitatively for magnetic-neutron-scattering experiments in the paramagnetic phase of La2-xSrxCuO4 when second-neighbor hopping is included. However, the peak positions, which in two dimensions are determined mostly by the band structure, cannot agree quantitatively with the experimental results when concentration-independent band parameters are used. More importantly, while the energy scale of roughly 150 K seen in the experiments can come from second-neighbor hopping, it arises most naturally if one is very close to a magnetic instability. The proximity to a magnetic instability can be checked experimentally by measuring the relative size of the lattice equivalent of 2k(F) anomalies that appear closer to the origin in wave-vector space. Such lattice-2k(F) anomalies would allow magnetic neutron scattering to become a spectroscopic tool for the two-dimensional Fermi surface. Finally, exact results are also given for the imaginary part of the Lindhard function on the square lattice.