Electron-Hole Asymmetry of Quantum Collective Excitations in High-T_c Copper Oxides

We carry out a systematic study of collective spin- and charge excitations for the canonical single-band Hubbard, $t$-$J$-$U$, $t$-$J$ models high-temperature copper-oxide superconductors, both on electron- hole-doped side phase diagram. Recently developed variational wave function approach, combined with expansion in inverse number fermionic flavors, is employed. All three exhibit substantial electron-hole asymmetry magnetic excitations, robust paramagnon emerging hole-doping, agreement available resonant inelastic $x$-ray scattering data cuprates. The model yields additional high-energy peak spectrum that not unambiguously identified spectroscopy. For all considered Hamiltonians, dynamical susceptibility contains coherent mode hole- electron doping, overall bandwidth renormalization controlled by on-site Coulomb repulsion. Away from strong-coupling limit, antiferromagnetic ordering tendency more pronounced electron-doped