1. Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, Department of Physics, Graduate School of Science and Center for Interdisciplinary Research (CIR), Tohoku University, Sendai 980-8578, Japan, CREST, Japan Science and Technology Corporation (JST), Kawaguchi 332-0012, Japan, Chevron Research and Technology, Richmond, California 94802, and Institute for Materials Research (IMR), Tohoku University, Sendai 980-8577, Japan