1. National Laboratory of Solid State Microstructures Jiangsu Key Laboratory of Artificial Functional Materials College of Engineering and Applied Science Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 China
2. Department of Materials Science and Engineering Pennsylvania State University State College PA 16802 USA
3. Materials Research and Technology Department Luxembourg Institute of Science and Technology (LIST) Avenue des Hauts‐Fourneaux 5 Esch/Alzette L‐4362 Luxembourg
4. Departament de Física Universitat Politècnica de Catalunya Campus Nord B4‐B5 Barcelona E‐08034 Spain
5. Department of Physics and Materials Science University of Luxembourg 41 Rue du Brill Belvaux L‐4422 Luxembourg
6. Institut de Ciència de Materials de Barcelona ICMAB‐CSIC Campus UAB Bellaterra 08193 Spain
7. Department of Physics Southern University of Science and Technology Shenzhen 518055 China
8. Department of Materials Science and Engineering and Department of Physics and Astronomy University of California, Irvine 916 Engineering Tower Irvine CA 92697 USA