Theory of two-particle excitations and the magnetic susceptibility in high-Tc cuprate superconductors

Two-particle (2-p) excitations such as spin and charge excitations play a key role in high-Tc cuprate superconductors (HTSC). On the basis of a parameter-free theory, which extends the Variational Cluster Approach (a recently developed embedded cluster method) to 2-p excitations, the magnetic excitations of HTSC are shown to be reproduced for a Hubbard model within the relevant strong-coupling regime. In particular, the resonance mode in the underdoped regime, its intensity, ''hour-glass'' dispersion and doping dependence are in good overall agreement with experiments. Combined with the earlier results for the phase diagram and one-particle excitations, such as the electron-hole asymmetry in the doping dependence of AF and SC phases and the presence of a gap dichotomy of the nodal and antinodal SC gaps, a consistent picture emerges, which lends substantial support to Hubbard-model descriptions of high-Tc cuprate superconductivity.