V.A.S., Y.Y., L.W.M., C.D., L.-Q.C., H.W., V.G. and J.W.F. acknowledge support from the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award Number DE-SC-0012375 for the development of the materials and ultrafast experiments. Z.H., S.L. and G.A.S acknowledge support from the National Science Foundation (DMR-1210588) and National Science Foundation Center for Nanoscale Science grant number DMR-1420620. L.-Q. C. also acknowledges support from NSF DMR-1744213. Use of the Advanced Photon Source was supported by the US Department of Energy, Office of Science, under contract no. DE-AC02–06CH11357. PFM data were collected at PSU, University of California, Berkeley, and at the Center for Nanophase Materials Sciences, a DOE Office of Science User Facility at ORNL. N.L. acknowledges support from the Eugene P. Wigner Fellowship at Oak Ridge National Laboratory (ORNL), a US Department of Energy (DOE) facility managed by UT-Battelle, LLC for US DOE Office of Science under contract no. DE-AC05–00OR22725. R.R. and L.W.M. acknowledge funding from the Gordon and Betty Moore Foundation’s EPiQS Initiative, under grant GBMF5307. NL acknowledges use of the Compute and Data Environment for Science (CADES) at the Oak Ridge National Laboratory. V.A.S. would like to thank C.M. Schlepütz and J. Hammonds for their development of rsMap3D, valuable discussions with H. Zhou, S Kalinin, Q. Li, Y. Ren, J. Tischler and D.D. Fong, and C.A. Kurtz for technical support.