title: Competing orders in FeAs layers.
abstract: Using the unrestricted Hartree-Fock approximation and Landau theory we identify possible phases competing with superconductivity in FeAs layers. We find that close to half-filling the transition from the paramagnet to the magnetically ordered phase is first order, making anharmonicities relevant and leading to a rich phase diagram. Between the already known one-dimensionally modulated magnetic stripe phase and the paramagnet we find a new phase which has the same structure factor as the former but in which magnetic moments at nearest-neighbor sites are at right angles making electrons acquire a nontrivial phase when circulating a plaquette at strong coupling. Another competing phase has magnetic and charge order and may be stabilized by charged impurities.
authors.affiliation: SMC-INFM-CNR and Dipartimento di Fisica, Università di Roma "La Sapienza," Piazzale Aldo Moro 2, 00185 Roma, Italy.
authors.forename: J
authors.initials: J
authors.lastname: Lorenzana
authors.forename: G
authors.initials: G
authors.lastname: Seibold
authors.forename: C
authors.initials: C
authors.lastname: Ortix
authors.forename: M
authors.initials: M
authors.lastname: Grilli