This work was supported in part by the AFOSR YIP programme, LEAST (one of the SRC/DARPA supported centres within the STARNET initiative), ASCENT (one of the SRC/DARPA supported centres within the JUMP initiative), and the Berkeley Center for Negative Capacitance Transistors and the Multicampus Research Programs and Initiatives (MRPI) of the University of California. Electron microscopy experiments and equipment were supported by the Cornell Center for Materials Research, through the National Science Foundation MRSEC programme, award DMR 1719875. The work at Penn State was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under award FG02-07ER46417. Z.J.H. acknowledges support from NSF-MRSEC grant number DMR-1420620 and NSF-MWN grant number DMR-1210588. R.R. and S.D. acknowledge support from the Gordon and Betty Moore Foundation’s EPiQS Initiative, under grant GBMF5307. R.R. also acknowledges funding from the Army Research Office. J.I. acknowledges support from the Luxembourg National Research Fund under grant C15/MS/10458889 NEWALLS. P.G.-F. and J.J. acknowledge financial support from the Spanish Ministry of Economy and Competitiveness through grant number FIS2015-64886-C5-2-P, and P.G.-F. acknowledges support from Ramón y Cajal grant no. RyC-2013-12515.

Reviewer information

Nature thanks D. Jiménez, J. Rondinelli and the other anonymous reviewer(s) for their contribution to the peer review of this work.