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TUE: Tuesday Contributed Sessions

TUE 12: Quantum Sensing and Decoherence: Contributed Session to Symposium III

TUE 12.2: Talk

Tuesday, September 9, 2025, 14:30–14:45, ZHG105

A nonlinear extension of crystallography - X-ray-optical wavemixing on valence charges — •Dietrich Krebs — Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany

As we celebrate 100 years of Quantum Physics, the field of x-ray crystallography simultaneously approaches its 111th anniversary. Both fields are closely intertwined - with innumerable advances in solid-state and quantum physics being propelled by crystallography's outstanding ability to determine the structure of matter microscopically. Yet, crystallography itself never quite progressed into the quantum realm. Instead, it largely remains a method rooted in concepts of classical waves and (spherical) charge densities.

In this talk, we outline how ideas from nonlinear optics and the use of modern x-ray free-electron lasers (XFEL) help to extend crystallography to the next order, namely nonlinear crystallography. Basing this extension on x-ray-optical wavemixing, it offers atomic-scale resolution - similar to regular x-ray crystallography - combined with the spectroscopic sensitivity of optical techniques. We present our results from a recent XFEL-experiment, which demonstrate the feasibility of nonlinear crystallography on laser-excited diamond. In particular, we showcase the 3D-reconstruction of the newly accessible valence-response function, which agrees well with our theoretical predictions from non-relativistic Quantum Electrodynamics.

Keywords: Wavemixing; nonlinear scattering; crystallography; diamond; QED