A magnon scattering platform

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 118; no. 25; p. 1
• Main Authors: Zhou, Tony X., Carmiggelt, Joris J., Gächter, Lisa M., Esterlis, Ilya, Sels, Dries, Stöhr, Rainer J., Du, Chunhui, Fernandez, Daniel, Rodriguez-Nieva, Joaquin F., Büttner, Felix, Demler, Eugene, Yacoby, Amir
• Format: Journal Article
• Language: English
• Published: Washington National Academy of Sciences 22.06.2021; Proceedings of the National Academy of Sciences
• Subjects: CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; condensed matter physics; Crystallography; DNA structure; ENGINEERING; Magnetic properties; Magnetometers; magnetometry; magnon; Magnons; Material properties; MATERIALS SCIENCE; Physical Sciences; quantum sensing; scattering; Surface waves; Thin films; Wave propagation; Wavelengths; X-ray scattering; Yttrium; Yttrium-iron garnet
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.2019473118

Significance This work describes a general scattering platform that uses magnons to explore the underlying properties of target materials. In this work we show how both phase and amplitude of magnons can be imaged using a nitrogen vacancy center magnetometer and how the scattered pattern of waves can be used to infer geometric and magnetic properties of a target material. To demonstrate this new experimental methodology we use a permalloy disk as our target and show that even with such a simple target unexpected behavior is observed. In addition, we provide a theoretical framework to reconstruct the properties of the target. Scattering experiments have revolutionized our understanding of nature. Examples include the discovery of the nucleus [R. G. Newton, Scattering Theory of Waves and Particles (1982)], crystallography [U. Pietsch, V. Holý, T. Baumback, High-Resolution X-Ray Scattering (2004)], and the discovery of the double-helix structure of DNA [J. D. Watson, F. H. C. Crick, Nature 171, 737–738]. Scattering techniques differ by the type of particles used, the interaction these particles have with target materials, and the range of wavelengths used. Here, we demonstrate a two-dimensional table-top scattering platform for exploring magnetic properties of materials on mesoscopic length scales. Long-lived, coherent magnonic excitations are generated in a thin film of yttrium iron garnet and scattered off a magnetic target deposited on its surface. The scattered waves are then recorded using a scanning nitrogen vacancy center magnetometer that allows subwavelength imaging and operation under conditions ranging from cryogenic to ambient environment. While most scattering platforms measure only the intensity of the scattered waves, our imaging method allows for spatial determination of both amplitude and phase of the scattered waves, thereby allowing for a systematic reconstruction of the target scattering potential. Our experimental results are consistent with theoretical predictions for such a geometry and reveal several unusual features of the magnetic response of the target, including suppression near the target edges and a gradient in the direction perpendicular to the direction of surface wave propagation. Our results establish magnon scattering experiments as a platform for studying correlated many-body systems.