1 School of Chemical and Physical Sciences, The MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, P.O. Box 600, Wellington 6140, New Zealand. thomas.nann@vuw.ac.nz.
2 Department of Physics, University of California Davis, One Shields Avenue, Davis, CA 95616-5270, USA. chiang@physics.ucdavis.edu.