1. Department of Physics, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K.
2. Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge CB3 0AS, U.K.
3. Center for Transformative Science, ShanghaiTech University, Shanghai 201210, China
4. School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, U.K.
5. Diamond Light Source, Harwell Science and Innovation Campus, Fermi Avenue, Didcot OX11 0DE, U.K.
6. London Centre for Nanotechnology, University College London, London WC1E 6BT, U.K.
7. Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11793, United States