Speaker
Description
Fluctuating field theory is a recently developed method for the description of competing collective fluctuations in correlated electron systems, able to account for spin, charge, and superconducting instabilities. On the basis of a variational principle, the method allows to explicitly account for the leading collective modes and their interplay, with access to electronic and spectroscopic properties. Extending its prior application to the Hubbard model at half-filling, we investigate its description of the doped Hubbard model, accounting for various spin instabilities. We show that unlike for Néel ordering, which dominates near half-filling, the phase structure of the fluctuating fields for collective instabilities with arbitrary ordering vector Q become important, expressing the modulation of the ordering relative the underlying lattice geometry. We observe the method, despite its weak-coupling rot, to give an efficient tool beyond mean-field theory to investigate a plethora of insulating and conducting magnetic phases with commensurate and incommensurate ordering vectors emerging within the phase diagram.