1. School of Engineering and Science, Jacobs University Bremen, 28759 Bremen, Germany
2. Division of Materials Science, Nara Institute of Science and Technology, 630-0192 Ikoma, Nara, Japan
3. CEA Laboratoire d’electronique des technologies de l’information, 38054 Grenoble, France
4. Geballe Laboratory for Advanced Materials, Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States