L. J. P. Ament

Resonant inelastic x-ray scattering studies of elementary excitations

In the past decade, resonant inelastic x-ray scattering (RIXS) has made remarkable progress as a spectroscopic technique. This is a direct result of the availability of high-brilliance synchrotron x-ray radiation sources and of advanced photon detection instrumentation. The techniques unique capability to probe elementary excitations in complex materials by measuring their energy, momentum, and polarization dependence has brought RIXS to the forefront of experimental photon science. Both the experimental and theoretical RIXS investigations of the past decade are reviewed, focusing on those determining the low-energy charge, spin, orbital, and lattice excitations of solids. The fundamentals of RIXS as an experimental method are presented and then the theoretical state of affairs, its recent developments, and the different (approximate) methods to compute the dynamical RIXS response are reviewed. The last decades body of experimental RIXS data and its interpretation is surveyed, with an emphasis on RIXS studies of correlated electron systems, especially transition-metal compounds. Finally, the promise that RIXS holds for the near future is discussed, particularly in view of the advent of x-ray laser photon sources.

Theoretical Demonstration of How the Dispersion of Magnetic Excitations in Cuprate Compounds can be Determined Using Resonant Inelastic X-Ray Scattering

L.J.P. Ament, G. Ghiringhelli, M. Moretti Sala, L. Braicovich and J. van den Brink Institute-Lorentz for Theoretical Physics, Universiteit Leiden, 2300 RA Leiden,The Netherlands INFM/CNR Coherentia and Soft – Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy Institute for Molecules and Materials, Radboud Universiteit Nijmegen, 6500 GL Nijmegen, The Netherlands Stanford Institute for Materials and Energy Sciences, Stanford University and SLAC National Accelerator Laboratory, Menlo Park, CA 94025. (Dated: March 17, 2009)

Creating and verifying a quantum superposition in a micro-optomechanical system

Micro-optomechanical systems are central to a number of recent proposals for realizing quantum mechanical effects in relatively massive systems. Here, we focus on a particular class of experiments which aim to demonstrate massive quantum superpositions, although the obtained results should be generalizable to similar experiments. We analyze in detail the effects of finite temperature on the interpretation of the experiment, and obtain a lower bound on the degree of non-classicality of the cantilever. Although it is possible to measure the quantum decoherence time when starting from finite temperature, an unambiguous demonstration of a quantum superposition requires the mechanical resonator to be in or near the ground state. This can be achieved by optical cooling of the fundamental mode, which also provides a method to measure the mean phonon number in that mode. We also calculate the rate of environmentally induced decoherence and estimate the timescale for gravitational collapse mechanisms as proposed by Penrose and Diosi. In view of recent experimental advances, practical considerations for the realization of the described experiment are discussed.

Momentum Dependence of Orbital Excitations in Mott-Insulating Titanates

High-resolution resonant inelastic x-ray scattering has been used to determine the momentum dependence of orbital excitations in Mott-insulating LaTiO(3) and YTiO(3) over a wide range of the Brillouin zone. The data are compared to calculations in the framework of lattice-driven and superexchange-driven orbital ordering models. A superexchange model in which the experimentally observed modes are attributed to two-orbiton excitations yields the best description of the data.

Bimagnon studies in cuprates with resonant inelastic x-ray scattering at the O K edge. I. Assessment on La2CuO4 and comparison with the excitation at Cu L-3 and Cu K edges

We assess the capabilities of magnetic resonant inelastic x-ray scattering (RIXS) at the O

Determining the electron-phonon coupling strength from Resonant Inelastic X-ray Scattering at transition metal L-edges

K

Observation of phonons with resonant inelastic x-ray scattering

edge in undoped cuprates by taking La

Ultrashort Lifetime Expansion for Indirect Resonant Inelastic X-ray Scattering

{}_{2}

Theory of resonant inelastic x-ray scattering in iridium oxide compounds: Probing spin-orbit-entangled ground states and excitations

CuO

Magnetic excitations in La2CuO4 probed by indirect resonant inelastic x-ray scattering

{}_{4}