The ability to control the structure of a crystalline solid on ultrafast timescales bears enormous potential for information storage and manipulation or generating new functional states of matter [1]. In many materials where the ultrafast control of crystalline structures has been explored, optical excitation pushes materials towards their less ordered high temperature phase [2{9] as electronically driven ordered phases melt and possible concomitant structural modifications relax. Nonetheless, for a few select materials it has been shown that photoexcitation can slightly enhance the amplitude of an electronic ordering phenomenon (i.e. its electronic order parameter) [9{13]. Here we show via femtosecond hard X-ray diffraction that photodoping of the perovskite EuTiO3 transiently increases the order parameter associated with a purely structural [14] phase transition represented by the antiferrodistortive rotation of the oxygen octahedra. This can be understood from an ultrafast charge-transfer induced reduction of the Goldschmidt tolerance factor [15], which is a fundamental control parameter for the properties of perovskites
@article{arxiv.1901.08388,
title = {Ultrafast transient increase of oxygen octahedral rotations in a perovskite},
author = {M. Porer and M. Fechner and M. Kubli and M. J. Neugebauer and S. Parchenko and V. Esposito and A. Narayan and N. A. Spaldin and R. Huber and M. Radovic and E. M. Bothschafter and J. M. Glownia and T. Sato and S. Song and S. L. Johnson and U. Staub},
journal= {arXiv preprint arXiv:1901.08388},
year = {2019}
}