title: Direct observation of dynamic charge stripes in La2-xSrxNiO4.
abstract: The insulator-to-metal transition continues to be a challenging subject, especially when electronic correlations are strong. In layered compounds, such as La2-xSrxNiO4 and La2-xBaxCuO4, the doped charge carriers can segregate into periodically spaced charge stripes separating narrow domains of antiferromagnetic order. Although there have been theoretical proposals of dynamically fluctuating stripes, direct spectroscopic evidence of charge-stripe fluctuations has been lacking. Here we report the detection of critical lattice fluctuations, driven by charge-stripe correlations, in La2-xSrxNiO4 using inelastic neutron scattering. This scattering is detected at large momentum transfers where the magnetic form factor suppresses the spin fluctuation signal. The lattice fluctuations associated with the dynamic charge stripes are narrow in q and broad in energy. They are strongest near the charge-stripe melting temperature. Our results open the way towards the quantitative theory of dynamic stripes and for directly detecting dynamical charge stripes in other strongly correlated systems, including high-temperature superconductors such as La2-xSrxCuO4.
authors.affiliation: Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309-0390, USA.
authors.forename: S
authors.initials: S
authors.lastname: Anissimova
authors.affiliation: Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309-0390, USA.
authors.forename: D
authors.initials: D
authors.lastname: Parshall
authors.affiliation: Condensed Matter Physics & Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA.
authors.forename: G D
authors.initials: GD
authors.lastname: Gu
authors.affiliation: Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: K
authors.initials: K
authors.lastname: Marty
authors.affiliation: Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Lumsden
authors.affiliation: Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Songxue
authors.initials: S
authors.lastname: Chi
authors.affiliation: 1] Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA [2] Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996-1200, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Fernandez-Baca
authors.affiliation: Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: D L
authors.initials: DL
authors.lastname: Abernathy
authors.affiliation: CEA Saclay, Laboratoire Léon Brillouin, F-91191 Gif sur Yvette, France.
authors.forename: D
authors.initials: D
authors.lastname: Lamago
authors.affiliation: Condensed Matter Physics & Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Tranquada
authors.affiliation: Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309-0390, USA.
authors.forename: D
authors.initials: D
authors.lastname: Reznik