Implications of Resonant Inelastic X-ray Scattering Data for Theoretical Models of Cuprates

摘要

There are two commonly discussed points of view in theoretical description ofcuprate superconductors, (i) Cuprates can be described by the modified t-Jmodel. (ii) Overdoped cuprates are close to the regime of normal Fermi liquid(NFL). We argue that recent resonant inelastic X-ray scattering data challengeboth points. While the modified t-J model describes well the stronglyunderdoped regime, it fails to describe high energy magnetic excitations whenapproaching optimal doping. This probably indicates failure of the Zhang-Ricesinglet picture. In the overdoped regime the momentum-integrated spin structurefactor S(\omega) has the same intensity and energy distribution as that in anundoped parent compound. This implies that the entire spin spectral sum rule issaturated at \omega ~ 2J, while in a NFL the spectral weight should saturateonly at the total bandwidth which is much larger than 2J.