Studies of light and matter interactions in the x-ray regime have long been instrumental to the advancement of condensed matter physics, lifted by synchrotron radiation sources that deliver high-throughput x-ray photons. Today, widespread initiatives exist to add the element of spatial coherence to the x-ray beam, which is believed could render new information about the nature of quantum matter at various spatiotemporal scales. However, there are still open questions about how the beam’s coherence can be utilized in clever ways to yield completely new information. In this talk, we show a possibility of exploiting the coherence in a completely new way. By confining the sampling to a simple spatial structure with only a few elements, a well-defined Fourier transform is easy to track (like a slit interference pattern). This simplification occurs naturally at the onset of a first order phase transition when domains begin to form.
Using resonant coherent x-ray diffraction (RCXD), we study the formation of antiferromagnetic domains in the correlated antiferromagnet PrNiO3. We demonstrate that it is possible to quantitatively extract the arrangements and sizes of the first-formed domains from single resonant coherent x-ray diffraction patterns. At the onset of the antiferromagnetic transition, the ordered domains are dilute in the beam spot, thus resulting in relatively simple coherent diffraction patterns, which can be inverted manually through a combination of visual inspection, system knowledge and trial and error. The success of our analysis suggests that a resonant Bragg coherent diffractive imaging approach with iterative phase retrieval algorithms may be effective in studying both these and even more complex antiferromagnetic spin textures. As an outlook, we argue that the same approach could be extended to a time-structured light source in order to study the motion of dilute dynamically driven domains, or to track the motion of topological defects in an antiferromagnetic spin texture.
Speaker: Alex Frano, UC San Diego
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