Date of Award

12-2013

Degree Name

Doctor of Philosophy

Department

Physics

First Advisor

Dr. Clement Burns

Second Advisor

Dr. Diego Casa

Third Advisor

Dr. Arthur Mcgurn

Fourth Advisor

Dr. Lisa Paulius

Keywords

Polarization analyzer; inelastic scattering x-ray; HOPG; bend silicon

Abstract

Resonant inelastic x-ray scattering (RIXS) is a powerful technique in condensed matter physics for studying the electronic excitations in novel materials of interest. In currently operating hard x-ray RIXS instruments the energy and momentum transfers are measured while the outgoing polarization is not measured due to significant technical challenges. But the outgoing polarization of the scattered photons provides valuable information (excitation symmetry) about the states involved in the scattering which is difficult to determine without polarization analysis. Polarization analysis has proved extremely valuable in soft x-ray RIXS, and so a polarization analysis system is being developed to fill the technical void at higher energies.

A polarization analyzer is designed to reflect the scattered photons from the main analyzer by about 90 degrees. At this reflecting angle, the in-plane polarization is naturally eliminated by the polarization factor so that the scattered photons perpendicular to the reflection plane are fully obtained. Therefore it can separate the two orthogonal polarizations (named ‘π’ and ‘σ’) by rotating the system by 90 degrees.

The research in this dissertation is about the development of an outgoing polarization analysis system complementing for the current RIXS instrument at Advanced Photon Source (APS). The polarization analysis system developed includes the x-ray polarization analyzer and the mechanics attached to the RIXS spectrometers and for aligning the polarization analyzer. A variety of diffraction-based polarization analyzers are being developed for different x-ray absorption edges. A polarization analyzer for Cu K-edge has been developed, and one for the Ir L3-edge has also been developed.

By separating the outgoing polarization, the strong polarization dependent electron excitations, e.g. the spin-orbital excitations in iridates can be measured by the polarization analysis system. Further, the system enables us to separate and study the transverse and longitudinal magnons in Sr2IrO4, demonstrating a new capability for the RIXS technique.

Access Setting

Dissertation-Open Access

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