1. Stephenson Institute for Renewable Energy and Department of Physics, University of Liverpool, Liverpool L69 7ZF, U.K.
2. Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, U.K.
3. Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
4. Felix Bloch Institute for Solid State Physics, Universität Leipzig, Leipzig, Germany
5. Lawrence Livermore National Laboratory, Livermore, California 94550, United States