Speaker
Description
Transient grating with EUV and soft X-rays has recently emerged as a powerful way to excite and detect nanoscale dynamics. Short penetration depths at these wavelengths have generally limited these experiments to thin films in a transmission geometry. In reflection, near normal incidence, the signal is entirely dominated by surface displacements. Here, we show that soft X-ray TG in a grazing incidence geometry enhances the sensitivity to permittivity changes, including electronic, elastic, and magnetic responses by up to four orders of magnitude in the soft X-ray regime. The enhancements for 1) refractive index gratings and 2) magnetic gratings are shown in Figs. A,B and Figs. C,D, respectively. We derive the angular dependence and enhancement of these contributions from Maxwell’s equations and detail important considerations for grazing incidence experimental geometries. Specifcally, we discuss the effect of grazing incidence on the pump efficiency, and important changes to the momentum conservation condition due to the presence of significant in-plane momentum at grazing angles. In addition, we show experimental results which demonstrate that at grazing incidence, magnetic responses can be on the same scale as surface displacement signals. These results greatly extend the applicability of soft X-ray TG to bulk samples, opening up many new avenues for studies of nanoscale phenomena. We envision that this geometry can be used, for example, to study charge transport in biomaterials, nanoscale magnetic dynamics in antiferromagnetic and altermagnetic crystals, and elastic dynamics on bulk and single-crystalline materials, to name a few.
| Scientific Topics | Solid State Physics |
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