X-ray transient grating spectroscopy at X-ray free electron lasers

Place: Conference room (IMDEA Nanociencia) and online (Zoom)

Link: https://nanoscience-imdea.zoom.us/j/99208427038

Abstract: 

Transient grating spectroscopy is a background-free time resolved four wave mixing technique that is widely used in the optical domain to gain information on transport and diffusion processes [1,2] as well as on vibrational, charge and magnetic dynamics of the ground or excited state [3-5]. In the past decade significant efforts has been undertaken to extend this technique into the extreme ultraviolet range permitting studies in solids on charge transport, coherent phonons, and ordering dynamics of the spin system at their intrinsic nanometer spatial and femtosecond time scale [6]. Extension of transient grating spectroscopy to X-rays would allow to overcome the limitations of the longer wavelengths by reaching the ultimate time and spatial resolutions (sub-femtosecond – sub-nanometer) with high momentum transfer, adding chemical specificity while the deep penetration will allow to study of both the surface (reflection) and bulk (transmission) properties. Very recently, we have proposed a relative simple method to the expand the application range of transient grating spectroscopy far into the X-ray domain. This technique uses a single transmission grating to generate the transient excitation pattern in the sample without involving complicated split-and-delay lines [7]. In a series of milestone experiments at X-ray Free Electron Lasers (XFELs) we have demonstrated the validity of the technique by generating X-ray transient gratings and probing with an optical laser [8] and with X-rays [9]. Our results open the possibility to apply X-ray transient grating to perform studies on semiconductors, magnetic materials, strongly correlated and quantum materials, disordered systems and chemical compounds. It will also  provide a robust tool to design and realize new functional materials with desirable properties such as for example high-temperature superconductors, ultrafast magnetic switches, nano-thermal devices, photo-to-electro catalysis, ultrafast non-volatile memory storage. In this talk I will present our first experimental results and give a perspective on the upcoming steps in the development of the X-ray nonlinear spectroscopies.

References

[1] Rogers, J.A., Maznev, A.A., Banet, M.J. et al. Annu. Rev. Mater. Sci., 30, 117–157 (2000) [2] Hofmann, F., Short, M., & Dennett, C. MRS Bulletin, 44(5), 392-402 (2019)

[3] Brown, E.J., Zhang, Q. & Dantus J. Chem. Phys. 110, 5772–5788 (1999)

[4] Torchinsky, D., Mahmood, F., Bollinger, A. et al. Nature Mater 12, 387–391 (2013)

[5] Janušonis, J., Jansma, T., Chang, C. et al. Sci Rep 6, 29143 (2016)

[6] Bencivenga, F., Cucini, R., Capotodi, F. et al. Nature 520, 205–208 (2015)

[7] Svetina C., Mankowsky R., Knopp, G. et al. Opt. Lett. 44 574–577 (2019)

[8] Rouxel, J.R., Fainozzi, D., Mankowsky, R. et al. Nat. Photon. 15, 499–503 (2021)

[9] Svetina, C., et al. In preparation