Simultaneous Study of Structure and Correlation-Driven Transitions via X-ray Standing Waves*

The possibility of decoupling electronic phenomena from those of the lattice has been a hot topic when discussing correlated metal-insulator transition materials such as VO₂, NbO₂, or V₂O₃.[1] A mainly electronic transition could enable ultra-fast switching, thin film electronics, with little risk of the inevitable physical degradation associated with bulk structural transitions. However, the roles of structural (Peierls) and electron correlation (Mott) effects in driving these transitions continue to be debated in the literature.[2] Using x-ray standing waves (XSW) and high quality epitaxial thin films, we have now concurrently investigated both the structural and electronic transition within some of these correlated materials using a single technique, directly measuring their simultaneity or lack thereof for the first time. We discuss these results and their wider implications.

[1] Kalcheim, Y. et al. Robust Coupling between Structural and Electronic Transitions in a Mott Material. Phys. Rev. Lett. 122, 57601 (2019).
[2] Lee, W. C. et al. Cooperative effects of strain and electron correlation in epitaxial VO₂ and NbO₂. J. Appl. Phys. 125, 082539 (2019).