National Synchrotron Light Source Seminar
"High Resolution Soft X-Ray RIXS in Quasi One-Dimensional Cuprates and Oxide Heterostructures"
Presented by Thorsten Schmitt, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
Wednesday, August 10, 2011, 9:30 am — Seminar Room, Bldg. 725
Resonant inelastic X-ray scattering (RIXS) is a powerful bulk-sensitive photon-in/photon-out spectroscopic probe of the electronic structure with atomic and orbital sensitivity. It is an ideal method for studying excitations from the electronic ground state in correlated transition metal oxides, being directly sensitive to charge-, orbital- and spin-degrees of freedom. Ultra-high resolution instrumentation for RIXS is available at the ADvanced RESonant Spectroscopies (ADRESS) beamline of the Swiss Light Source at the Paul Scherrer Institut, being optimized for soft X-rays with variable polarization between 0.4 and 1.8 keV . The SAXES (Super Advanced X-ray Emission Spectrograph) RIXS spectrometer of the ADRESS beamline has a resolving power of ca. 12000 for 1 keV. It allows varying the scattering geometry between incident and inelastically scattered X-rays in order to study low-energy excitations as a function of momentum transfer. In this talk I will give an overview on high-resolution and momentum dependent RIXS studies of magnetic and electronic excitations in quasi one-dimensional cuprate and oxide hetersotructure systems
Sr2CuO3 is a quasi one-dimensional corner-sharing single-chain compound possessing the nearly ideal properties of the one-dimensional antiferromagnetic Heisenberg spin-1/2 model. The momentum transfer dispersion of the Cu L3-RIXS signal in Sr2CuO3 along the chain direction reveals that the main spectral weight follows the lower onset of the two-spinon (and higher order) continuum and probes the dynamical spin structure factor. Numerical calculations within the Bethe Ansatz allow a detailed line shape analysis of the RIXS response. The modes within the orbital excitation energy range show that the dd excitations in Sr2CuO3 are momentum dispersive and can be associated with orbitons, i.e. dispersive excitations mediated by the superexchange interactions. A spin-orbital superexchange model reproduces this orbiton dispersion and explains the lar
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