[1] Cavendish Laboratory, Department of Physics, University of Cambridge, J J Thomson Ave., Cambridge CB3 0HE, United Kingdom
[2] Los Alamos National Laboratory, Los Alamos, NM 87545, United States
[3] University of Minnesota, Minneapolis, MN 55455, United States
[4] Sumation Co. Ltd., 2020 Cambourne Business Park, Cambourne, Cambridgeshire CB23 6DW, United Kingdom
[5] Cambridge Display Technology Ltd., Building 2020, Cambourne Business Park, Cambridgeshire CB3 6DW, United Kingdom