title: Spin excitations of ferronematic order in underdoped cuprate superconductors.
abstract: High-temperature superconductors exhibit a characteristic hourglass-shaped spectrum of magnetic fluctuations which most likely contribute to the pairing glue in the cuprates. Recent neutron scattering experiments in strongly underdoped compounds have revealed a significant low energy anisotropy of these fluctuations which we explain by a model in which topological defects of the antiferromagnet clump to producing domain wall segments with ferronematic order. This state does not invoke global charge order but breaks C4 rotational and inversion symmetry. The incommensurability of the low doping charge-disordered state is in good agreement with experiment and interpolates smoothly with the incommensurability of the stripe phase at higher doping. Within linear spin-wave theory the dynamic structure factor is in very good agreement with inelastic neutron scattering data and can account for the observed energy dependent anisotropy.
authors.affiliation: Institut für Physik, BTU Cottbus-Senftenberg, PBox 101344, 03013 Cottbus, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Seibold
authors.affiliation: ISC-CNR, CNISM and Dipartimento di Fisica, Università di Roma "La Sapienza", P.le Aldo Moro 5, I-00185 Roma, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Di Castro
authors.affiliation: ISC-CNR, CNISM and Dipartimento di Fisica, Università di Roma "La Sapienza", P.le Aldo Moro 5, I-00185 Roma, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Grilli
authors.affiliation: ISC-CNR, CNISM and Dipartimento di Fisica, Università di Roma "La Sapienza", P.le Aldo Moro 5, I-00185 Roma, Italy.
authors.forename: J
authors.initials: J
authors.lastname: Lorenzana